This article considers the political nature of public space and explores its psychological relevance as a natural arena of citizenship. Drawing on literature in social psychology, environmental psychology, and political geography, the article addresses how common understandings of normative behavior in public are often based on particular constructions of place and people-space relations. In so doing, it shows how such culturally shared “locational” notions are essentially contested in relation to their political significance and ideological orientation within a particular public socio-spatial context. It is argued that claims for and demands on public space are enshrined in broader struggles over the psychological boundaries of belonging, identity, and civic entitlements which are central to the contentious issue of citizenship. This is illustrated through the analysis of an emblematic struggle over a public space located in the Old Town of Barcelona between 1999 and 2007, triggered by the social appropriation of an undeveloped urban lot. The article pinpoints how considering the material dimension of public space may also enrich existing psychological approaches to citizenship.