Abstract
A conceptual blind spot in prevailing models of metropolitan regions is how to understand urbanisation in secondary localities that evolve to be neither an ideal-typical suburb nor a city. This article foregrounds Nick Phelps’ notion of ‘interplaces’ to provide this missing link in our understanding of metropolisation. Interplaces are defined as localities which are situated in between the conventional conceptual and geographical boundaries of the city and the suburb that significantly shape the patterns of economic, political and cultural activity across the metropolitan region. Whereas existing research on interplaces has isolated categories such as post-suburbs and shadowed cities, we argue for a more structured and granular vocabulary that captures their full diversity and, in the process, reveal intermediary types such as the ‘metrotown’. Our novel framework categorises the variety of interplaces according to their different roles resulting from their partial and uneven spatial-functional, political-institutional and cultural-symbolic integration in the metropolitan region. The framework is illustrated by studying three interplaces in the metropolitan area of Brussels, Belgium. The analysis shows that while interplaces may defy easy categorisation, their hybrid, rapidly evolving and sometimes contradictory nature makes them central to understanding the materialisation of metropolitan regions at a larger spatial scale. In so doing, we lay the foundation for more context-sensitive urban theory and governance approaches that better reflect contemporary (sub)urban realities.
Introduction
It is now widely recognised that traditional urban models – organised around the idea of cities surrounded by suburbs and rural hinterlands – are inadequate to describe the functionally complex and polymorphous landscape of contemporary metropolitan regions. Concepts such as the Zwischenstadt (Sieverts, 2003), the ‘Edgeless City’ (Lang, 2003), the desakota (McGee, 1991), the ‘nebular city’ (Van Meeteren et al., 2016) and the città diffusa (Indovina, 2016) denote how metropolitan regions, alongside their historic cities, also consist of an in-between space in which localities simultaneously exhibit urban and suburban qualities (Tzaninis and Boterman, 2018). These in-between spaces may seem mundane, but they are often the most dynamic parts of metropolitan regions in terms of population dynamics (Moreno-Monroy et al., 2021), shifting economic activities (Phelps, 2004), new forms of governance (Phelps et al., 2010) and clashing metropolitan and local identities (Terlouw, 2024; Van Damme et al., 2024).
Despite these shifts, research on metropolitan regions often remains stuck in a city-centric logic. For example, a large stream of literature on polycentric urban regions has studied how multiple core cities in a region come to operate as a functionally, politically and culturally integrated whole (Derudder et al., 2022). However, polycentricity research provides only a partial picture of metropolitan integration, as it tends to focus on a select number of core cities, while relegating the often-complex places in between to the conceptual, analytical and empirical background (Cardoso and Meijers, 2021).
Scholars have proposed paying more attention to the ‘interplaces’ between established urban centres (Phelps, 2017; Phelps et al., 2023) to achieve a more comprehensive analysis of regional urbanisation processes. Drawing on this body of research, we define interplaces as: Localities that are significant shapers of economic, political, or cultural activity within a metropolitan region, which are functionally linked to, and are physically located in-between, multiple metropolitan (sub)centres and exhibit characteristics that are neither fully urban nor suburban.
Two strands of literature, each representing a specific type of interplace, engage critically with these localities. The post-suburbanisation literature discusses the functional, political and cultural emancipation of suburbs into post-suburban centres on the outskirts of city-regions (Keil, 2020; Phelps et al., 2023). These post-suburbs obtain this emancipation through borrowed size effects, selectively lending urban features from their larger neighbours (Meijers and Burger, 2017). In parallel, a body of literature has developed around how formerly functionally independent secondary cities become increasingly functionally, politically and culturally interwoven by the core city of a metropolitan region (Mayer et al., 2021; Pendras and Williams, 2021). In some cases, the secondary city loses its prestige and functions to the primary node. Inspired by the notion of ‘agglomeration shadows’ (Meijers and Burger, 2017; Partridge et al., 2009), we term this subset of secondary cities ‘shadowed cities’. In the literature, post-suburbs and shadowed cities tend to be treated separately. We argue, however, that they represent two types along a wider spectrum of interplaces that simultaneously possess urban and suburban characteristics. Furthermore, within the research on post-suburbia and shadowed cities, scholarship remains compartmentalised along specific dimensions such as their socio-demographic diversification (Tzaninis, 2020), shifting employment structures (Aritenang, 2023), evolving amenity bases (Meijers and Cardoso, 2021), paradoxical political properties (Jonas, 2011), variable civic capacities (Hytrek, 2021), contradictory aesthetic-symbolic representations (Keil, 2015) and ambivalent cultural significance (Michel, 2024). An integrated perspective that jointly considers these different functional, political and cultural dimensions can deepen the theorisation of interplaces.
The concept of ‘metropolisation’ offers a useful framework for structuring these fragmented perspectives. Cardoso and Meijers (2021) understand metropolisation as the gradual and uneven process through which spatially fragmented places become integrated at a higher spatial scale along a spatial-functional, a political-institutional and a cultural-symbolical dimension. Despite their emphasis on providing a more holistic view of how different dimensions of metropolisation unfold beyond ‘the city’, applications of the metropolisation framework have hitherto remained focused on the metropolitan region as a whole – for example, by examining their shifting boundaries across dimensions (Nelles, 2021). Its principles can nevertheless be extended through an urban systems approach (Van Meeteren, 2019). This implies analysing how specific places within the region are differentially affected by the regional-scale processes of functional, political and cultural metropolisation and linking these developments to those in other localities of the region.
Against this backdrop, this article develops a more comprehensive vocabulary for the interplaces that shape metropolitan regions. In doing so, we aim to recognise interplace diversity rather than reducing them to a uniform category, an essential step towards generating precise analytical insights and context-sensitive policy interventions. To tackle this objective, we first adapt Cardoso and Meijers’ (2021) theory on metropolisation into a framework that explains how spatial-functional, political-institutional and cultural-symbolic integration partially and unevenly unfolds in interplaces. We subsequently position post-suburbs and shadowed cities within this framework while highlighting a third, intermediate category in the process. We then illustrate the framework in the metropolitan area of Brussels, Belgium. Brussels is particularly instructive given the city-region’s peculiar metropolisation trajectory, where strong opposing integrative forces produce and are shaped by distinct and sometimes contradictory places. Our in-depth discussion of three such interplaces, which only partially align with existing categories, underscores the necessity of a more comprehensive vocabulary. Finally, we reflect on these findings and outline a research agenda to further explore the significance of interplaces in metropolitan settings.
Interplaces and the tripartite process of metropolisation
The term ‘interplaces’ denotes places that play a significant role in metropolitan economic, political or cultural activities but are nonetheless positioned outside the primary urban cores (Phelps, 2017). However, Phelps’ (2017: 15–40) depiction of interplaces covers substantial conceptual variation to isolate the ‘economy in-between’. To undergird the concept empirically, we need a more focused urban-geographical conceptualisation. Cardoso and Meijers’ (2021) theoretical framework on ‘metropolisation’ provides a useful entry point to clarify how interplaces manifest themselves. They conceptualise metropolisation as a process entailing three complementary and intertwined dynamics that together weave individual places into a more integrated overarching metropolitan system. The first dimension is generated through increased spatial-functional interdependencies between places. These changing interdependencies result from a spatial reorganisation and redistribution of economic activities and specialised amenities, which in turn modulate daily mobility across the metropolitan area. The second dimension refers to how metropolitan governance organisations enable erstwhile peripheral places to gain political-institutional capacities which allow a redistribution of regional agglomeration benefits towards these places. The third dimension refers to the cultural-symbolic unification process of the metropolitan region, where multiple places start to collectively function as cultural and symbolic reference points of the region in the minds of inhabitants and external observers.
Importantly, the qualities traditionally associated with cities are potentially redistributed across many localities within the metropolitan region rather than a select number of core cities. In addition, the tripartite process of metropolisation is inevitably an uneven and long-term process without a clear endpoint, implying differential spatial coverage, intensity and rhythms of change. As a result, the three metropolisation processes do not necessarily converge in the same localities and/or at the same moment. Instead, urban qualities are claimed by different places at different intensities and thus occur in multiple, incomplete combinations (Cardoso and Meijers, 2021; Poorthuis and Van Meeteren, 2021).
In other words, metropolitan integration leads to the emergence of and differentiation among the interplaces that constitute the metropolitan region. This interplay of integration and differentiation within the expanding metropolitan region (Van Paassen, 1962) could imply both the gaining of functional, political or cultural urban qualities through borrowing size as well as losing them in agglomeration shadows (Meijers and Burger, 2017). Crucially, the intra-regional distribution of gains and losses is not spatially neutral but systemically linked: the advancement of one locality in terms of functional, political or cultural centrality often coincides with the relative marginalisation or peripheralisation of another (Jonas, 2012).
Interplaces can then be conceptualised as localities that partially and/or unevenly possess the spatial-functional, political-institutional and cultural-symbolic qualities associated with cities due to their ongoing integration in the metropolitan system (Figure 1).
The process of the integration of and differentiation among interplaces in a metropolitan region.
During metropolisation, interplaces can exhibit partial urban characteristics within a particular dimension of integration, fulfilling a function that is neither perfectly suburban nor urban. For instance, a place like Croydon, once an independent market town but now integrated in London’s built-up area, has developed as both a residential suburb and an employment centre when considering its spatial-functional centrality. Hosting London’s first commercial airport and major office complexes by the 1960s, Croydon gained the economic stature of a provincial city while simultaneously retaining its role as a suburb of London (Phelps, 1998). Moreover, interplaces are unevenly integrated as their (sub)urban qualities become variously aligned across the different dimensions of integration. For example, an airport city such as Schiphol in the Netherlands is a significant employment centre in the Randstad region and may thus be considered ‘urban’ in terms of its spatial-functional centrality. Yet, it lacks the vibrant population necessary to host the diverse social and cultural activities that characterise urban ways of life from a cultural-symbolic perspective (Bontje and Burdack, 2011). Conversely, a historic town such as Toledo – situated in the metropolitan area of Madrid – may uphold its image as an important (inter)national cultural centre and its political function as a provincial capital but is largely overshadowed by Madrid in terms of its regional economic capacity (Solís Trapero et al., 2015).
Together, these two examples underline the wide variety how localities take on a role as interplaces. We thereby explicitly refer to interplaces as ‘localities’ that are not (territorially) discrete, bounded or self-contained (Jones and Wood, 2013), but rather open and porous sub-systems shaped by multiple urbanisation processes (Keil and Macdonald, 2016). While we focus on frictions within regional-scale processes, a multi-scalar perspective highlights how processes at other scales also contribute to their formation and contested character. For instance, airport interplaces (like Schiphol) are not only key regional economic nodes but also sites where global mobility, national infrastructure policy and local environmental concerns intersect (Addie, 2014) so that they, and interplaces more generally, are best understood as what Lepawsky et al. (2015) term ‘site multiples’: places assembled through diverse and sometimes contradictory practices defying a singular interpretation.
The intertwined processes that render localities into more complex sub/urban forms often follow diverse trajectories of structural change. As Phelps and Wood (2011) observe, these include both the transformation of suburbs into post-suburban formations and the gradual relegation of secondary cities into dormitory settlements for nearby urban centres – we refer to the latter as ‘shadowed cities’ moving forward. While the literatures on post-suburbs and shadowed cities are well established, we outline below how they represent distinct yet interconnected positions as interplaces within the tripartite metropolisation process.
The post-suburb and shadowed city: Two crowded points on an interplace spectrum
To conceptualise this diversity of interplaces, we introduce a stylised 3-by-3 framework (Figure 2). The rows represent different dimensions of metropolisation, whereas the columns illustrate how places may experience shadowing, borrowing or a hybrid of both as outcomes of their integration and differentiation in the metropolitan region.
The 3-by-3 framework summarising the different possible characteristics of interplaces in metropolitan regions.
Although any combination of borrowing and shadowing across these components is theoretically possible, certain patterns are more common than others. Post-suburbs tend to borrow economic functions through a higher-than-expected employment role but remain shadowed in political influence and cultural recognition, much like traditional suburbs (Bontje and Burdack, 2011). Hence, their characteristics are unevenly aligned across the dimensions of metropolisation (yellow tiles in Figure 2). Shadowed cities, on the other hand, typically exhibit the obverse: they retain political and cultural centrality while being increasingly overshadowed in spatial-functional terms (Pendras and Williams, 2021; red tiles in Figure 2). In addition, a third, intermediary category between the post-suburb and shadowed city, tentatively conceptualised as ‘metrotowns’ for ease of referencing, illustrates partial integration as more complex, hybrid combinations of borrowing and shadowing take place (blue tiles in Figure 2).
The boundaries between these three interplace categories are inherently fuzzy. Indeed, interplaces may be assembled in ways that blur or stretch the distinctions presented here. We therefore view our proposed types as heuristic reference points to facilitate a more structured discussion of interplaces, rather than as monolithic categories that exclude other combinatory types or processes not captured by our framework.
The spatial-functional characteristics of interplaces
First, the post-suburbanisation of former suburbs involves the socio-economic diversification in suburban outskirts of large cities, transforming traditionally dormant suburbs into centres of employment and social diversity (Keil, 2020). As centrifugal forces increasingly push economic activities into these places that were until then located peripherally in the city’s hinterland (Champion, 2001), these suburbs grow into post-suburban centres. The economic foundations of post-suburban interplaces largely stem from market-driven processes compelling firms to seek out new locations in the relative vicinity of the city, or from endogenous economic development due to increased local amenities. Firms increasingly cluster in ‘mundane’ places that are well connected to an urban core, allowing them to borrow size from the agglomeration while avoiding high rents and congestion (Phelps, 2004). Similarly, service functions like retail, commerce and entertainment activities are increasingly moving from the urban core to the suburbs (Kubeš and Ouřední ček, 2022). Geographically peripheral yet well-connected office parks, retail centres and shopping malls are emblematic of the uneven expansion of the city-region’s economic geography. As a consequence, compared to ‘regular’ suburbs, post-suburbs are characterised by functional diversification, a broadening economic base and increased employment opportunities.
Second, shadowed cities are a particular type of historic secondary city (Pendras and Williams, 2021) that have become incorporated into the metropolitan region (Champion, 2001) and subsequently ‘regress into suburbs or dormitory settlements for nearby cities’ (Phelps and Wood, 2011: 2594). This transformation leads functionally relatively self-contained cities to become increasingly integrated with, and orientated towards, other centres for functions they previously held independently. Hence, a shadowed city may experience a spiral in which it ‘los[es] its identity as economically significant, [is] more dependent on the nearby city, los[es] (economic) activity during workdays as well as depend[s] solely on tax revenue from residents’ (Mayer et al., 2021: 57). In other words, the nearby metropolitan centres increasingly cast an agglomeration shadow onto the city, which gradually attains the spatial-functional characteristics of a suburb. Nonetheless, a shadowed city may remain a distinctively urban place of residence for households that currently live and work in other urban centres, developing the tax base necessary to become a regional service centre itself with high-end amenities for affluent residents (Williams and Pendras, 2025). Indeed, instead of retreating to the suburbs, it has recently been found that inhabitants of nearby urban centres increasingly prefer to ‘hop over’ to places that ‘tend to be well connected and rich in functions and that have historical urban character and identity’ (Meijers and Cardoso, 2021: 50).
Despite their opposing trajectories, the post-suburb and shadowed city both defy a straightforward definition as either urban or suburban. Moreover, their similarities in terms of outcome draw attention to a third category intermediate to these two well-described types. We refer to these as metrotowns. These are particularly relevant in (but not limited to) European settings where historic small and medium-sized market towns or provincial centres remain institutionally distinct but become functionally enmeshed in the metropolitan system. They are not formed by a purely ‘centrifugal’ or ‘incorporation’ formation mode (Champion, 2001; Münter and Volgmann, 2021) but rather through a ‘blended’ version (Solís Trapero et al., 2015), whereby recent waves of post-suburban development are deposited onto the historically urbanised settlement landscape (Van Meeteren et al., 2016). This selective recombination leads to the sorts of hybrid assemblages that effectively render a type of place conceptually situated in between the post-suburb and the shadowed city, one where urbanisation and suburbanisation are simultaneously at play (Demazière, 2022). Unlike typical post-suburbs, however, the dense, mixed-use town centre and layered built environment of metrotowns is paired with an independent civic or administrative identity, and unlike shadowed cities, they have retained or regained relevance as employment hubs, secondary service nodes or transport interchanges.
Croydon exemplifies such a metrotown. Once a market town and later a site of significant manufacturing and large-scale post-war office development, it now functions as a key employment node within Greater London while always having been severely constrained by Central London in terms of its development (Phelps, 1998). In re-reading his earlier work, Phelps (2017: 110) initially frames Croydon as a post-suburb but soon highlights its historical urban character, illustrating the difficulty of fitting such places into existing urban–suburban categories. This underscores the conceptual ambiguity of metrotowns not only in functional terms but also politically and culturally.
The political-institutional integration of interplaces
The political-institutional capacities of interplaces do not always match their spatial-functional centrality. As metropolisation generates societal benefits and costs, political imbalances in the region determine which places bear the brunt. The distribution of costs and benefits could tilt to either the periphery or the core, depending on the historical context and the degree of jurisdictional independence of the interplace.
Post-suburban interplaces are often truly caught ‘in between’ jurisdictions and thus become easily overlooked and shadowed by the dominant metropolitan policy regime (Young and Keil, 2014). In such scenarios, policy makers ‘struggle to advance their particular interests over those of core jurisdictions’, thus leading to ‘political and economic capacities of peripheral areas [which] are not yet mature’ (Salet and Savini, 2015: 449). In other contexts, post-suburbs can continue to be ‘parasitical’ on the core city, sapping away the urban tax base and services (Teaford, 1997) or engaging in horizontal governance arrangements in order to secure Funding from higher tiers of government (Nelles, 2013).
Shadowed cities typically occupy a more central position in decision making as they operate within a clearly defined jurisdiction and retain inherited political influence. To ease the pressures of a growing residential base and, in some cases, a declining industrial economy, local officials may choose to engage more actively in city-regional politics, aiming to capture and direct some of the regional agglomeration benefits to their advantage (Meili and Mayer, 2017; Pendras and Williams, 2021). However, recent explorations of the subject in France, England and Italy show that shadowed cities may struggle not to be subordinated to the interests of the primary city once encapsulated in a metropolitan governance structure (Cotella et al., 2024), further pointing to the fuzzy boundaries between these seemingly ideal-type interplaces when it comes to borrowing and shadowing political performance. Alternatively, interplaces may therefore participate in governance networks that explicitly exclude the core city to counterbalance its political dominance and build an agenda that advances their own interests instead (Casavola et al., 2024), essentially borrowing political size from each other and shadowing the core.
A similar dynamic can also be observed in the former suburbs of European metropolitan regions which tend to have historically ‘urban’ political complexions as they were once autarkic towns or villages with their own local institutions, governments and political agendas (Charlesworth and Cochrane, 1994; Phelps and Wood, 2011). These metrotowns may be able to leverage their relative political centrality to cause a gradual shift away from traditional suburban-style politics to a new, somewhat paradoxical form of ‘post-suburban new regionalism’. In this approach, they selectively engage with the core to support metropolitan growth objectives when it benefits their local economy but oppose it when it threatens to affect their exclusionary suburban character (Jonas, 2011), pointing to a hybrid combination of political borrowing and shadowing. Greater Toronto’s Greenbelt policy exemplifies this ambivalence. Enacted to limit inner-city sprawl into the outer ‘suburbs’, it was paired with a targeted growth strategy that allowed post-suburban densification in designated zones leading to heavy negotiations around its spatial demarcation (Keil and Macdonald, 2016). The governance of metropolitan regions is thus not solely marked by centre–periphery dynamics but also by a continuous spatial negotiation between multiple metropolitan centres. Considering broader implications for metropolitan governance, the Toronto case illustrates that greater awareness of the systemic interdependence and the ‘in-between’ political positioning of interplaces – and metrotowns in particular – is achievable, even in policy areas where decisions are otherwise framed through a binary urban–suburban lens. More generally, in policy domains where functional, political and cultural metropolitan change are tightly interwoven, such as housing or transport infrastructure development (Young and Keil, 2014), close and balanced interjurisdictional coordination may prevent interplaces’ developments from being shaped solely by decisions made elsewhere.
In sum, interplaces can exhibit multiple and sometimes contradictory pathways towards political-institutional (de)centrality. Their jurisdictional delineation influences their capacity to assert political agency, while the forms of metropolitan cooperation they engage in determine the extent of their integration into, or separation from, the broader metropolitan region.
The cultural-symbolic integration of interplaces
All interplaces undergo transformations that reshape local place identities and perceptions about the metropolitan region as a relevant object of identification. The urban symbolism embedded in the built environment is a key factor in this process. Similarly, the rapidly changing demographics of interplaces imply that distinct local identities increasingly coexist with fluid, cosmopolitan identities, creating tensions in how interplaces are perceived among different groups of inhabitants (O’Connor and Wynne, 1996).
Although post-suburban developments like corporate office complexes, shopping malls or intermodal transit hubs project an ‘urban’ image, they often lack the recognisable qualities of historic cities with their heterogeneity and associated urban charm (Augé, 1995). Hence, these places represent seemingly ‘placeless’ extensions of the city, their essence being difficult to pinpoint by their population and external observers alike (Nüssli and Schmid, 2016). Some of these new peripheral centralities (Phelps et al., 2023) may obtain their own cultural identity within the metropolitan region as an ‘edge city’, often combining their enhanced urban-economic centrality with a distinctively defiant anti-urban cultural identity (Beauregard, 1995; Garreau, 1991). In other contexts, rather than creating recognisable symbols of their own, the cultural image of the nearby and clearly identifiable city extends into the post-suburbs, leading to the emergence of a wider metropolitan place identity (Kübler, 2018). The two cultural identities may also clash. For example, Nüssli and Schmid (2016) note that, in the post-suburban Glattal area of northern Zurich, new socio-political contradictions are unfolding between new residents who mainly view these spaces as an extension of the Zurich metropolis and long-time residents who continue to cling to an idyllic, explicitly localised image of their place of residence.
Shadowed cities, on the other hand, typically project a distinctly urban image rooted in their legacy as historic cities. Even as their spatial-functional centrality declines, they ‘maintain a degree of independent history and identity that mitigates against uncritically collapsing them into the mass of the “city-region” ’ (Pendras and Williams, 2021: 2). Nonetheless, here too, the influx of new residents may introduce contrasting representations of place, especially when newcomers are of different ethnicities and bring a more cosmopolitan image to public space (Tzaninis, 2020). Residents whose daily activities span multiple areas within the metropolitan region may perceive the region as a cohesive and meaningful space, using several interconnected places rather than a single location as key reference points.
Indeed, a more culturally hybrid pathway is one where interplaces ‘become post-suburban in terms of their economic function, [but] remain suburban in terms of the imaginations of their residents (Teaford, 1997)’ (Phelps et al., 2006: 31). Rapid changes in the built environment may be perceived as a threat to suburban lifestyles, reinforcing small-town identities and anti-urban development positions (Ruming et al., 2025). Terlouw’s (2024) example of Muiden in the vicinity of Amsterdam clearly shows how this dynamic plays out in a metrotown. This small historic city has been incorporated into Amsterdam, even to the point that its signature medieval castle was for a while renamed ‘Amsterdam Castle’ for tourist consumption. Muiden is functionally entirely suburbanised, yet its residents have developed a resistance mentality against the metropolitan region based on a rural reading of their own historical identity. As such, Muiden may seem shadowed by Amsterdam for external observants, yet locals’ sense of identity strengthens as a result thereof.
In sum, the cultural-symbolic integration of different types of interplaces into a wider metropolitan region reveals that the reconfiguration of their image and local identity is both simultaneously linked to and distinct from the core city and involves a complex interplay of traditional and cosmopolitan identities among diverse resident groups.
Exploring the interplaces of the Brussels metropolitan area
Building on the theoretical exploration of how interplaces can gain or lose centrality amid metropolisation, we now examine these dynamics empirically in the metropolitan area of Brussels, Belgium. The Brussels-Capital Region (BCR) and its surrounding functional urban area exhibit a complex interplay of integration and fragmentation across spatial-functional, political-institutional and cultural-symbolic dimensions (Figure 3). After painting a general picture of the three dimensions of metropolisation in the larger Brussels metropolitan region, we focus on how their interplay plays out in three Flemish municipalities (Zaventem, Aalst and Vilvoorde), summarising their characteristics as interplaces in Figure 4.
Overview of the (a) spatial-functional, (b) political-institutional and (c) cultural-symbolic integration of the Brussels metropolitan area.
Summary of the functional, political and cultural characteristics of Zaventem, Vilvoorde and Aalst.
Spatial-functionally, the urban agglomeration and functional urban area of the BCR extend well beyond its administrative boundaries, encompassing municipalities in both the Flemish and Walloon Regions (Vanderstraeten and Van Hecke, 2019). This area has a historically dense settlement geography, with numerous small and medium-sized towns functioning as anchor points of subsequent phases of urbanisation (Grosjean, 2012). Since the 1950s, suburbanisation has continued unabated. From the 1980s onwards, economic activity gradually shifted away from the declining industrial hubs along the Brussels canal zone (e.g. Vilvoorde) and the Dender Region (e.g. Aalst), an economic transition which was offset by Brussels’ resurgence as an international services hub alongside the emergence of new economic growth poles, most notably the airport northeast of the capital (e.g. Zaventem). Although Brussels remains the metropolitan area’s economic core, the gap between incoming and outgoing commuters has been steadily narrowing. The resulting spatial structure is therefore one which produces an extensive urban field with overlapping and entangled functional connections across its components (Van Meeteren et al., 2016).
Political-institutionally, the metropolitan area is marked by fragmentation due to Belgium’s federal state structure. Whereas the BCR has extensive powers over spatial policies, it only covers the territory of a historical snapshot of the urban agglomeration, with its periphery extending into the neighbouring Flemish and Walloon Regions (Kesteloot and Saey, 2002). These regions possess significant autonomy over policy domains that are crucial for metropolitan integration, including economic development, infrastructure, public transport, housing and spatial planning. Existing governance structures covering the Brussels functional urban area have gradually been dissolved because of stepwise federalisation since the 1970s. For instance, since 1996, the Flemish government has established the donut-shaped area of the ‘Flemish Periphery’ (Vlaamse Rand) in which it actively promotes policies aimed at containing the urban expansion of the Brussels ‘oil stain’, striving to preserve its green and Dutch-speaking character (Boussauw et al., 2013). Another example is the dissolution of the bilingual electoral district of Brussels–Halle–Vilvoorde during the sixth state reform of 2011. This reform effectively prevented French-speakers in the Flemish suburbs of Brussels from voting for predominantly French-speaking Brussels politicians, thus aiming to stop the ‘francisation’ of the Flemish Periphery. Despite the counterpromise to create a metropolitan governance structure integrating the BCR and its surrounding municipalities, such a framework has never materialised (Bonfiglioli, 2020).
Indeed, the political divide between the BCR and its surrounding Flemish municipalities is deeply ingrained in linguistic and cultural tensions between Dutch-speakers and French-speakers (Bonfiglioli, 2020). Officially bilingual, the BCR is predominantly French-speaking in practice, whereas the Flemish Region remains officially monolingual Dutch-speaking. Nonetheless, some municipalities in the Flemish Periphery of the BCR house a significant number of francophones. This has historically influenced their political organisation, leading to the establishment of language facilities that allow French speakers to receive official communications in French rather than Dutch, an artefact from state reforms in the 1960s (Vandermotten et al., 1990: 31). Each language community thereby has its own institutions, media and cultural networks which further exacerbate this cultural dichotomy (cf. Paasi, 1986; Sinardet, 2013). Migration, both international and internal, increasingly adds another layer to this tension. As of 2024, 77% of inhabitants of the BCR are non-Belgian nationals or Belgians with foreign roots, with English and Arabic being important daily languages. Although newcomers often first settle in the BCR, these predominantly non-Belgians and/or French-speakers subsequently settle in the Flemish Periphery (De Laet, 2018). This cultural expansion of the BCR leads to evolving cultural identities and, at times, tensions in the mostly white and Dutch-speaking surroundings. The contrast between Brussels’ multiculturalism and the small-town identities of the Flemish periphery has deepened anti-urban and anti-immigration sentiments (Van Damme et al., 2024), a shift reflected in the 2024 federal election victory of right-wing, Flemish-nationalist parties.
While the Brussels metropolitan area is significantly integrated in spatial-functional terms, political-institutional fragmentation and cultural-symbolic tensions between the BCR and the Flemish Region in particular present substantial challenges for cohesive metropolitan governance and identity formation. Against this backdrop, we now turn to how these divides are experienced differently in different interplaces in the metropolitan region.
Zaventem: A post-suburban interplace?
The municipality of Zaventem is best known for hosting Brussels National Airport. Economic activity as a freight and logistics hub has significantly increased since the 1990s (Strale, 2020). However, the municipality also houses numerous office complexes with advanced producer services firms (Waiengnier et al., 2020) as well as conference centres and event halls. As such, Zaventem is evolving from a mere transport hub to both a productive and consumptive centre that would qualify it as a typical example of an ‘airport city’. This post-suburbanity is also reflected by commuting patterns, with Zaventem having a larger daytime than nighttime population. A large portion of incoming commuters originates from the BCR, even leading to an inversion of the traditional commuting balance between suburb and city (Table 1). Indeed, Zaventem carves out its own labour market area within Brussels’ overarching sphere of influence (Van Meeteren and Boussauw, 2016), making it a typical case of a post-suburban interplace which borrows its spatial-functional centrality from the wider metropolitan region.
Indicators of the spatial-functional, political-institutional and cultural-symbolic integration and centrality of the discussed interplaces.
As part of the Flemish Periphery, Zaventem is firmly committed to containing the expansion of the BCR, a sentiment reflected in the 2024 federal elections where one third of the population voted for Flemish-nationalist parties (Table 1). Yet, its economic reliance on airport-related tax revenue, the Flemish government’s push for airport expansion and the BCR government’s wish to alleviate unemployment by improving public transport connectivity to the employment centres of the airport, drive local officials to support further growth and increased connectivity with the BCR. Here, the ongoing construction of a tramline between the BCR and the airport is a case in point. While such interregional infrastructure projects typically get bogged down in lengthy and tedious negotiation processes between the local and regional governments involved, its construction underscores the fact that interregional cooperation is possible when policy visions align. As such, it is a rare occasion of political-institutional metropolisation in an otherwise politically segregated context (Cassiers, 2018). It is nonetheless telling that the trajectory of the tramline will connect the working-class neighbourhoods of the BCR to Zaventem’s office complexes and airport facilities only, bypassing its affluent suburban neighbourhoods. Thus, Zaventem’s policy objectives reflect those of a metrotown, seeking to borrow size from the metropolis by pursuing economic growth and drawing on support from higher government tiers (Flemish and BCR), while at the same time resisting the shadow of the BCR to preserve its exclusive suburban character (Jonas, 2011).
Zaventem’s cultural-symbolic characteristics nonetheless largely mirror those of the BCR. While its history as a small historic village predates the airport, it was never a historic city with strong symbolic significance. Today, it is primarily perceived as a transitory space shaped by airport connectivity at multiple scales, the name of the municipality being colloquially associated with the airport rather than the residential areas beyond. The latter nonetheless form a microcosm of Brussels’ cosmopolitan character. Some areas within the municipality have a significant French-speaking population, making up around 40% of residents (Bonfiglioli, 2020). The demography also reflects the internationalisation of Brussels, with a mix of Maghrebian migrants concentrated in the village centre and expatriates from mainly OECD countries settling in the more affluent neighbourhoods. Ultimately, Zaventem’s diversity and post-suburban landscape therefore reinforce the perception – both locally and externally – of it being an extension of the Brussels metropolis rather than a distinct cultural-symbolic entity of its own.
Overall, Zaventem can largely be seen as a post-suburb. However, given its specific institutional context – where it holds considerable agency and is not politically overshadowed by the metropolitan core – it also displays characteristics of a metrotown in political-institutional terms.
Aalst: A shadowed city?
Situated in the Dender region, Aalst is a formerly industrialised city with approximately 88,000 inhabitants. Since the 1970s, the city’s diminishing role as an industrial hub – combined with its strategic position between Brussels and Ghent and strong public transport accessibility – has led to its gradual transformation into a satellite city of both metropolitan centres. As the largest Belgian city unable to develop an independent functional urban area, Aalst is entirely overshadowed by Brussels’ metropolitan reach in spatial-functional terms (Vanderstraeten and Van Hecke, 2019). Indeed, its commuting ratio is nearly balanced, meaning it houses about as many commuters as it attracts. Commuting with the BCR is extremely uneven: most outgoing commuters work in the BCR whereas the opposite hardly occurs. Similarly, suburbanisation emanating from Aalst is largely absent as the city does not carve out its own housing market area (Van Meeteren et al., 2015: 60–61). Compared to the other interplaces, Aalst has a much lower employment ratio relative to its working population. Additionally, amenities have gradually diminished since the 2000s (Table 1). As such, it is an interplace, both in status and in geography, which is shadowed by and positioned between Brussels and Ghent.
In political-institutional terms, despite its de facto role as a satellite city, Aalst is recognised as one of Flanders’ 13 ‘central cities’ (centrumsteden), a political statute that comes with significant additional Funding from the Flemish government meant to alleviate metropolitan socio-economic burdens. Although not the provincial capital, Aalst functions as the geographical and political centre of the Dender Region, an intermunicipal structure meant to align cooperation in various policy domains. Here, containing Brussels’ metropolitan influence is high on the political agenda, as underscored by the coalition agreement of the Aalst city council: We do not want Brussels-like conditions here. […] Dutch is the language that unites us. Newcomers should integrate into the existing community and adopt our norms and values. Even in a rapidly changing world, we find it important to preserve the identity of our city. (Gemeentebestuur Aalst, 2024: 3)
This anti-metropolitan stance is endorsed by at least half of the inhabitants who voted for Flemish-nationalist parties – one of which holds seats in the city council and is attributable to the statements above. Ironically, the leapfrog population spillovers from Brussels into places like Aalst are themselves the result of similar urban containment policies implemented in municipalities directly bordering Brussels, especially the one disguised as a greenbelt strategy in the Flemish Periphery. These have not contained metropolitan pressures but merely displaced them (Boussauw et al., 2013). In sum, despite Aalst’s ongoing spatial-functional integration in the metropolitan region, it continues to operate as a city that is formally politically independent from yet also experiencing the ripple effects of decisions made in and around the BCR.
In cultural-symbolic terms, Aalst has managed to retain its own distinct identity, characterized by its strong Dutch-speaking community and rich local heritage dating back to medieval times. This is reflected in local traditions such as the Carnival of Aalst, which was recognized between 2010 and 2019 as UNESCO intangible cultural heritage. The city experiences fewer linguistic tensions compared to municipalities in the Flemish Periphery, yet it has seen the largest proportional influx of non-Dutch speakers and non-Belgians among the studied areas (Table 1). While the Flemish Periphery attracts the majority of working-class outmigrants from the BCR, Aalst stands out as the first municipality not directly bordering Brussels with the highest rate of in-migration. This trend is particularly notable among the lowest income decile of Brussels’ working-class municipalities, who have been drawn to Aalst more than to the surrounding Dender towns due to its efficient public transport connection to Brussels and Ghent, as well as the historic stock of low-cost labourer’s housing (De Laet, 2018). At the same time, a wave of urban-style apartment construction is underway to accommodate the growing population. Long-time residents often perceive these changes as a threat to Aalst’s traditional Flemish and small-town character (Van Damme et al., 2024). Although some still hold on to a strong local identity, this sense of place is increasingly challenged by newcomers and the city’s deepening integration into the broader metropolitan region.
Overall, Aalst largely aligns with the ideal type of a shadowed city – functioning as a satellite of Ghent and Brussels while resisting political subordination, especially to the latter. However, its evolving cultural-symbolic landscape increasingly resembles that of a metrotown, where diverging views between long-time residents and newcomers create internal tensions, and its once-distinct identity becomes gradually intertwined, particularly with the metropolitan character of Brussels.
Vilvoorde: Post-suburb, shadowed city or metrotown?
Vilvoorde, a small city of around 46,000 inhabitants located just 10 km from central Brussels in the Flemish Periphery, exemplifies a spatial-functionally hybrid interplace shaped by centuries of interdependent development with the BCR. In medieval times, Vilvoorde competed with Brussels for regional prominence, particularly in textile production, but it was gradually overshadowed from the 15th century onwards. It later re-emerged as an industrial hub along the Antwerp–Brussels–Charleroi axis – the spatial backbone at the height of Belgium’s industrialisation (Van Meeteren et al., 2016). Like many industrial cities, Vilvoorde severely suffered from deindustrialisation between the 1970s and 1990s. Since then, however, the city has partially modernised its economy by rebranding itself as a ‘media city’, attracting film studios and production companies, while also leveraging its position near Brussels Airport in Zaventem to develop a transport and logistics sector. Moreover, Vilvoorde has become a key node along a new tangential bus rapid transit line connecting post-suburban zones in the northeastern periphery of Brussels. Hence, its peripheral centrality and economic diversification have led to an overall positive commuting balance and rapid employment growth (Table 1). Yet, like Aalst, the city also faces challenges. Despite its partial economic revitalisation, its job ratio and commuting ties from Brussels remain modest, and it has experienced a significant decline in amenities since the 2000s. Rapid population growth, driven largely by Brussels’ suburbanites, adds further pressure to this transformation (Table 1). As such, Vilvoorde is a locality with intermediary qualities emerging from a field of tension between its function as both an agglomeration shadow and a post-suburb, whose economic centrality derives from simultaneous borrowing from and shadowing by Brussels and its surroundings.
This ambiguous centrality persists in political-institutional terms. Vilvoorde is one of two leading cities in the Halle–Vilvoorde region, a cooperation framework of Flemish municipalities territorially encircling yet excluding the BCR (Figure 3(B)). This regional framework aims to collectively ‘act as a “buffer” for Flanders in terms of encroaching internationalisation, the presence of non-Dutch speakers [and] migration from Brussels’ (Toekomstforum Halle–Vilvoorde, 2021: 56). Paradoxically, the region asserts itself as a ‘central region’ while simultaneously excluding Brussels from this centrality. Actual cooperation of Vilvoorde with the BCR exists only in limited, ad hoc cases where policy visions align, reflecting persistent scepticism towards deeper institutional cooperation – the deployment of the interregional bus rapid transit line being the exception that proves the rule. In other words, local policy objectives straddle the line between pursuing metropolitan integration and, at the same time, preserving an independent, small-town character (cf. Jonas, 2011; Phelps and Wood, 2011). Unlike Aalst, Vilvoorde does not enjoy ‘central city’ status, despite surpassing other central cities in population size and facing metropolitan challenges. The Flemish government has partially recognised these challenges by increasing Funding streams towards the municipality, yet it still falls short of the resources granted to officially recognised central cities, highlighting Vilvoorde’s liminal position between a fully acknowledged city and a mere satellite town of the BCR.
In cultural-symbolic terms, too, regional actors continually walk the line between affirming a distinct identity and defining that identity in relation to the dominant metropolitan pull of Brussels. For example, the Halle–Vilvoorde region is framed as ‘one coherent region with a distinct peripheral identity’ (Toekomstforum Halle–Vilvoorde, 2021: 56) – a formulation that inherently ties its alleged uniqueness to its peripherality to the capital. In Vilvoorde, the absence of political recognition is criticised by local politicians, as it is thought to undermine the city’s ability to maintain its cultural distinctiveness. The interplace’s former mayor stated in a newspaper interview that ‘without additional support from the Flemish and federal government, our city […] is heading straight towards an irreversible loss of identity as a Flemish city. If we continue down this path, we will soon become an integral part of the de facto Brussels living environment’ (Van Asbroeck, 2024). Implicitly referring to Vilvoorde as the primary destination for outmigrants from Brussels (De Laet, 2018), newcomers are often perceived as not integrating well into local life, using the town mainly as a residential anchor point for their professional and social lives in Brussels, which complicates efforts to engage them in the local community (Hendrickx, 2018). Consequently, internal divides emerge between those who view Vilvoorde as a mere suburb of Brussels and those who see it as a distinct local community.
In sum, the hybridity of Vilvoorde across all three dimensions of metropolisation – neither fully out of reach of the Brussels metropolitan area nor fully integrated with it, and neither central nor subsumed by it – highlights its ambiguous position as a metrotown which internalises the sometimes-conflicting characteristics of the post-suburb and the shadowed city.
Conclusion: Towards a fuller recognition of interplaces in metropolitan regions
This article proposed a new vocabulary for understanding the diversity of interplaces that partially and unevenly shape – and are shaped by – the metropolitan region. We introduced a 3-by-3 framework that classifies interplaces according to their varying degrees of borrowing and shadowing in relation to processes of metropolisation, defined here along the axes of spatial-functional, political-institutional and cultural-symbolic integration. While well-established categories such as post-suburbs and shadowed cities can be relatively easily positioned as ideal types on each of these axes, our framework introduces the metrotown, a category of interplaces characterised by more contradictory, intertwined dynamics of borrowing and shadowing.
This 3-by-3 framework is intentionally located on a meso level of abstraction. Our empirical exploration of interplaces in the Brussels metropolitan area lays the groundwork for a research agenda by identifying at least four ways in which the framework can be adopted and adapted in future studies.
First, the three theoretical examples of interplaces serve as heuristic reference points that align with neatly traceable combinations of functional, political and cultural borrowing or shadowing, but elucidate other potentially complex combinations in empirical reality. Indeed, the cases of Zaventem, Aalst and Vilvoorde broadly correspond to the three main interplace categories, yet all display a tendency towards borrowing political-institutional performance. This pattern reflects Belgium’s peculiar federalising state structure, which causes metropolitan disintegration in the political-institutional realm, leaving Brussels politically shadowed by its surrounding interplaces. Such alternative combinations of borrowing and shadowing can easily be positioned within the framework, along with others already hinted at in earlier scholarship. For example, Miao’s (2018) reading of the Tsukuba Science City in the Greater Tokyo area offers an insight into another peculiar type of ‘in-between place’. While Tsukuba borrows substantial political-institutional weight through its concentration of governmental and scientific institutions, it is a spatial-functional hybrid that is neither a suburb of Tokyo nor an independent city and remains cultural-symbolically shadowed due to its entirely planned-out character. Other interplaces could include former seats of government such as Versailles in Greater Paris or Potsdam near Berlin, places which have intermediate political and functional characteristics at best but function as important cultural-symbolic reference points within their respective metropolitan regions. We therefore encourage researchers to utilise our framework to classify interplaces based on their distinct characteristics of borrowing and shadowing and to explore other types of interplaces not discussed here.
Second, while our case studies have largely been framed as interplaces in relation to Brussels, this approach has somewhat masked their geographical in-betweenness (Phelps and Silva, 2017) – that is, their position within overlapping spheres of influence of multiple (sub)centres rather than a single primary city (Halleux et al., 2021; Poorthuis and Van Meeteren, 2021). For instance, Aalst is equally shadowed by the metropolitan reach of Ghent and the greenbelt policies in the Flemish Periphery. Likewise, nodes in the latter (i.e. Zaventem and Vilvoorde) are shaped not only by their relationship with Brussels but also by their mutual interdependence and connections with other cities in the polycentric metropolitan region, an area also known as the ‘Flemish Diamond’ (Albrechts and Lievois, 2004). Future research should therefore extend the urban systems approach presented here by analysing processes of borrowing and shadowing in relation not solely to a primary city but also to the metropolitan region in its entirety.
Third, our focus on interplaces as administratively delineated municipalities positioned relative to other such municipalities risks homogenising them as internally coherent. Rather, interplaces are ‘permeable organising containers’ (Phelps, 2017: 29), and an analytical reliance on municipal boundaries to analyse them risks overlooking the micro-level spatial processes that drive metropolisation (Poorthuis and Van Meeteren, 2021). Indeed, our findings suggest that the municipalities of Zaventem, Vilvoorde and Aalst are themselves composed of a mosaic of contrasting socio-spatial forms, covering both inner-city suburbs and high-end residential zones, former industrial estates and new enclaves of hypermobility, each of which are structured by forces operating at different scales – from local zoning decisions to global flows of labour. On a more theoretical note, and similar to the methodological sensibility suggested by Lepawsky et al. (2015), interplaces should therefore be viewed as what Jones and Woods (2013) have called ‘new localities’ that take shape in different spatial registers: in absolute space, as formally bounded administrative territories; in relative space, through their ties to each other as well as the overarching metropolitan system; and in relational space as assemblages whose transformation is largely contingent upon external forces such as global capital investment and migration. While we have mainly attended to the first two readings of interplaces, the relational dimension deserves further attention in the future.
The interplace concept in an urban-geographical register allows unifying insights from a plethora of related urban studies literatures in order to better understand the evolution of complex urban and metropolitan systems. To conclude, acknowledging the partial and uneven features of interplaces, their hybrid positions within metropolitan dynamics of borrowing and shadowing, and their geographical position in between the full register of metropolitan centres, as well as their multiscalar relationality and internal heterogeneity, offers a more robust foundation for advancing interplaces as a meaningful object of research.
Footnotes
Funding
The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The research for this article was supported by Research Foundation Flanders (FWO) under PhD number 11P8V24N.
Declaration of conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.