Unanticipated urban phenomena or “exceptions” in newly planned modernist cities of the twentieth century have mostly been conceptualized as contradictions to the ideal “plan.” An examination of the functioning and everyday life of these planned places, however, reveals that rather than being marginal dysfunctional phenomena, exceptions play a central role in the way abstract plans are operationalized and planned cities are experienced. For instance, in the planned modernist city of Islamabad, the capital of Pakistan designed in 1959 by Greek architect-planner C. A. Doxiadis, both marginalized and affluent communities routinely engage in exceptions in order to gain access to certain rights and privileges. By focusing on spatial exceptions found in Islamabad, I thus ask: What is the relationship between the plan and the exception in a planned modernist city? What are the similarities and differences found in the spatial and political tactics of different socio-economic groups engaged in creating exceptions? To answer the first question, I will investigate the proliferation of exceptions in the planned sectors in Islamabad in order to highlight the constitutive role they play in planned urban environments. To address the second question, I will conduct an historical analysis of both a squatter settlement and an unauthorized elite-housing neighborhood in Islamabad, attending to the differing ways each setting is partially constituted through spatial practices at variance with legally sanctioned rules. Using different ethnographic and archival methods to investigate these two main aspects, this research thus addresses the politics of creating a modernist space in Pakistan as they emerge in spatial practices and tactics located outside official planning protocols while nevertheless remaining critical to the functioning and organization of the city.