The analysis of two mosques built in the last fours years in Nantes reveals the effects of public policy on urban forms and expressions. Building a mosque implies inserting a new type of building in the city, a “foreign” type, more or less desired. Interpretations of the law, uses of regulations and municipal views of public space intertwine to shape a building that is most often split into two (with a religious and cultural part) and located far from the centre or residential neighbourhoods. These mosques provide a primarily symbolic anchoring for the Muslim community, as their atmospheres in public space are actually very limited.