Introduction

Until recently, it was rather common to perceive the hinterland of cities as ‘rural’, directing research to the study of linkages, relations and dependencies between ‘urban’ and ‘rural’ (for example, see Hoggart, 2005). This widespread traditional conception of cities having a predominantly rural hinterland needs to be challenged, as processes of spatial upscaling and expansion have made many cities find other cities in their hinterland, suggesting that a focus on regional urban–urban relations is just as valid as a focus on urban–rural relations. Put simply: many functional urban areas or metropolitan areas – terms traditionally used to denote a city and its surrounding commuting area – are nowadays composed of multiple cities. It makes sense to address these regions as multicentric urban areas or as ‘polycentric urban regions’ when these cities do not differ widely in terms of size or overall importance.

Champion (2001) has distinguished three modes through which such multicentric urban regions arise. First, he distinguished a ‘centrifugal mode’: some smaller cities in the sphere of influence of larger cities may have risen as satellite towns of the latter, as a result of core city expansion and redistribution. Second, an ‘incorporation mode’ is discerned when a larger city extends its sphere of influence to include a formerly rather selfsustaining surrounding town or small city, or a set of several such cities. Third, the ‘fusion mode’ denotes that previously distinct and independent cities of rather similar size become integrated due to the advancement of connective infrastructure and technology, and the spatial extension of activity and travel patterns of people and firms.

Basing our research on European Spatial Planning Observation Network (ESPON) data (projects 1.1.1 and 1.4.3 in particular; see ESPON, 2005, 2011), we can calculate that 1,001 out of the 1,967 European cities are actually located in a multicentric metropolitan area (meaning that they are located in the sphere of influence of another city and vice versa), whereas the others are the sole centre of their functional region. In terms of population, the share is even larger: out of the 265 million inhabitants of these 1,967 cities, almost 192 million people (72.4 per cent) live in a multicentric urban region, while only 73 million people live in cities that do not have other cities in their hinterland.