The space of the city is both a manifestation of social dualisms and an instrument through which they are maintained and reproduced. For several millennia, the Southeast Asian archipelago has been the site of some of the world’s most diverse urban juxtapositions of ethnicity and culture. While the bifurcation implied in the use of the term ‘social dualism’ may serve to characterize situations where the dominant set of social distinctions occur according to a single factor, the social conditions found in the history of Southeast Asia require a characterization that captures the non-linear, nonhomogeneous operation of multiple overlapping factors. A finely grained hierarchy of social distinctions has historically been mapped according to complex combinations of class, religion, ethnicity, language and occupation. Since the first centuries of the Common Era, trade has brought different populations together and towns have formed as a spatial mosaic of distinct ethno-linguistic cultures operating in explicitly segregated urban spaces. These often sharply defined enclaves offer a rich demonstration over time of ways in which social norms are negotiated, imposed, managed and reproduced in relation to specific physical forms of the built environment – a situation that might be usefully identified as exhibiting characteristics of heterotopia.