This contribution traces the evolution of the Belgian urban system by adopting an historical taxonomy of agglomeration-economy regimes, and poses the question whether a new centralizing agglomeration-economy regime based on renewed 'metropolization' can be observed. Belgium has federalized into three regions during the last decades, and different spatial perspectives emerged about how the central metropolitan area crosscuts the regional borders. After placing Belgian metropolization in its historical context, we engage with its contemporary geography. We inquire if the metropolitan core of Belgium is more akin to the 'Flemish Diamond', with capital city Brussels as the southernmost node, or whether a spatial pattern reminiscent of the historical 'Antwerp-Brussels-Charleroi (ABC)-Axis' is a more adequate description. To answer these questions, we examine the spatial integration of the Belgian labor market utilizing Vasanen's (2012) connectivity field method and a 2010 nation-wide travel-to-work dataset. The results indicate that contemporary metropolization in Belgium can be topographically expressed as an area that is more trans-regional than the Flemish Diamond yet more polycentric than an extension of Brussels, thus pointing to renewed economic centralization tendencies at the supra-regional level.1 Although part of a broader theoretical claim that remains unexamined in this chapter, Scott's (2012) claims about the emergence of a new 'cognitive-cultural economy' discusses the same agglomerative mechanisms as Krätke's (2007) 'metropolization'. 2 The term 'nebular city' ('nevelstad' in Dutch) was adopted from the Italian concept of città