The beginning of the middle Neolithic (from 4700 BCE onward) saw the development of new cultural changes in the upper Seine basin: the appearance of monumental burial places reserved for a handful of people marked the emergence of social elites which did not exist before. It was also in this period that the first enclosures appeared, usually delimited by a palisade trench and a discontinuous ditch. Located mainly in the valleys, these sites are less than five acres in area. Some seem to have been possible settlements, but others seem to have hosted periodical, ceremonial and/or festive gatherings. Enclosures increased in number in the second part of the middle Neolithic (from 4300 BCE onward), just when dug funerary monuments were disappearing; they attest to a significant growth in enclosed areas, usually between 12 and 25 acres, and sometimes up to 50-75 acres. The enclosures not only gained in size and complexity and in some cases acquired a defensive function. Buildings are sometimes located inside the enclosures, but their significance—everyday dwelling or places of exceptional events—remains a topic of discussion. Some of these enclosures also—in a second phase?—acquired a funerary function, with simple burials but no monuments. In the current state of research, the enclosures dating from the recent Neolithic (3500 to 2900 BCE) are few in number but highly diversified, ranging from small palisaded enclosures of less than 3 acres to gigantic constructions sometimes reaching 125 acres in area. The enclosures are larger than the earlier constructions, but the most significant among them gained in size and complexity, with a probably defensive and undoubtedly ostentatious brief. The numerous family and communal buildings inside the enclosure attest to the great variety of functions of these central sites, probably linked to their strategic position. Over and above functional issues, we should bear in mind the collective character of these constructions, whose building involved, for the largest among them, complex and major works and the mobilisation of large communities. Enclosures then seem to disappear from the landscape, giving way to other, notably funerary, monuments of a considerably smaller scale, possibly due to communities being more isolated.