The present article examines the particular role that cities have played, and should play, in global social history. It notes that many of the historiographical discussions that in the past years have addressed the reach and limits of the bourgeoisie and the middle class as a globalized social formation have implicitly focused on cities. It also notes that these discussions have often not been very forthcoming in explicitly acknowledging this urban focus. From this starting point, the present article ponders the implications and ramifications of making this focus more explicit. What do we conclude from the observation that the ‘global bourgeoisie’ or the ‘global middle class’, inasmuch as they existed at all, were quintessentially urban formations? And what do these conclusions, conversely, entail for the field of urban history? Highlighting density and differentiation as key traits of the urban form, the article ultimately argues for greater attention to the spatiality and to the built environment of class formation in global history.