In 1965, plans for building five new cities were implemented in the outskirts of Paris. Among these new cities, Melun-Sénart – the most recent of them – was not allowed to build its centre until 1985. In 1986, Melun-Sénart, by then called simply Sénart, launched an idea contest for the creation of its centre but the winning project wasn’t followed through. Instead, the city developer put forward a new project named the “Carré Sénart”. A 1.4km² area, it was designed to become the city centre. It was subdivided into an orthogonal framework in which most notably a shopping mall was inserted. It now draws ca. 10 million visitors each year and has become the city’s common space. This paper revisits the onset and development of the project so as to understand how a city project initially launched by the State ended up with a shopping mall as city centre.