Nouakchott, the Mauritanian capital city, has known a process of extremely rapid growth for the past thirty years. It translates into a continuous extension of the so-called periphery, where land occupation is irregular. Furthermore, urban programmes have been intensifying for some years, and projects of land regularisation and urban renovation have grown. These urban projects have generated a popular demand for land regularisation. Actors' strategies, generally individual, add up to produce a dynamics of structural shaping of the city. In this paper, I show how, in a town occupied by a first generation of settled and urban population, a land stake builds up, with its many actors and stakeholders, who manage to seize land plots from their official beneficiaries - to poor from the periphery - and to transform a non-market public domain into an intense land market. I will also show how the interplay of market forces and strategies, in a framework of resource and information inequalities, contributes to produce a city characterised by spatial segregation, which pushes the poorest to its outskirts.