A many-centred, multi-city, urban area of more than 10 million inhabitants, characterized by complex networks of economic specialization. Vicino et al. (2007) Int. J. Urb. Reg. Res. 31, 2, in a study of the US Bowash Megalopolis, reveal a complex socioeconomic pattern structured by class, education, housing tenure, housing age, and race and ethnicity. They identify distinct clusters: ‘affluent places’, ‘places of poverty’, ‘Black middle class places’, ‘immigrant gateway places’, and ‘middle America places’. The Metropolitan Institute Census Report Series 05:01 (2005) is an excellent resource on this.