This article explores the peri-urban dynamics in developing cities using a theoretical examination of the metropolis as the new urban condition. Although a western conceptualization, the notion of the metropolis, and particularly metropolitan planning, was exported to the developing world to address its urbanization problems. Metropolitan development authorities were established for wider city regions and accorded legislative powers to prepare master plans for the metropolitan areas. However, in most instances, their planning strategies resulted in a conflation of the urban–rural interface into a more complex peri-urban condition, marked by heterogeneity and fragmentation. The article illustrates this through an empirical investigation in the Indian city of Chennai, where socio-spatial transformations of two borderland neighbourhoods on its southern periphery are assessed mainly in terms of metropolitan planning decisions over the decades. In outlining their metamorphosis, the study is careful not to perceive such conflicts as simple forms of polarization between the rich and the poor. Rather, it sets the class conflicts against the politico-economic dynamics yielding newer forms of polarization in the peri-urban spaces.