In Nouakchott in Mauritania, as in all the Cities of the Global South, the demographic explosion has led to unbridled growth in peripheral zones. This process will continue in future decades when a new Afri- can urban population numbering hundreds of millions will not take up the gaps in the existing cities or even make them denser but will be forced to move onto completely unurbanised land. Jérôme CHENAL, head of the Urban and Regional Planning Community at the École Polytechnique Fédérale de Lausanne (EPFL), considers that the challenge currently facing African cities does not lie in the existing city or the city centre but in the outskirts.