Numerous researches, and more particularly in the field of migration and transnational mobility. However, studies of the impact of migrants on cities themselves remain insufficient. Based on ethnographic work within the United Nations office in Geneva, this paper argues that the impact of international civil servants on the city's settings and space lies in an expatriates' "ethnoscape" (APPADURAI, 1990) transforming Geneva's architecture, public space and patterns of sociability. The paper also analyses in what terms these urban mutations get contested in a central neighbourhood where inhabitants criticize gentrification, the rise of rental prices and eviction. Not only do the results of this study shed light on the process through which the presence of the UN office transforms Geneva in a global city, but they also show how such transformations of the urban space may produce the symbolic and spatial boundaries of contested territories that bring inhabitants to negotiate oppositional identities. In a broader theoretical perspective, this paper allow us to defend, along authors such as Boltanski and Thévenot, a pragmatist approach of boundaries, paying attention not only to their role in the discursive drawing of specific communities and public problems but their actual anchorage in every day practices. In other words, boundaries — in their various phenomenal manifestations — participates in the phenomenological and practical separation of contrasted urban worlds, that is of differentiated ways to organize — and relate to — urban everyday experience. This raises the question of how a boundary actually works as a separation and differentiation process, how it influences perceptions and actual experience of the world