The edge of the Quartier du Moulon is not a simple line, a demarcation boundary line embodying a temporary stabilization of the urban expanse. The edge area here widens and enriches itself until becoming the place where the reconciliation between two long opposed worlds, the city and the countryside, can take place again. The project site here becomes a magnificent laboratory for approaching the challenges involved in spatial transition of peri-urban territories. A position and awareness that constitutes as well one of our major contributions to the team led by Jean Nouvel for the international consultation regarding the Grand Paris project in 2009. This edge, with its surface area of around five hundred hectares is made up out of already existent landscape (Palaiseau public forest, Bois  (woods) of Normandie and Vaulhallan) as well as new landscape entities. The area is a composite landscape, a collection of contiguous spatial entities made up of varying sizes, typologies, functions, and means of being managed. This intermediate landscape is a small, domestic piece of countryside. The use of techniques and methods borrowed from the sphere of agriculture allows as well for the meeting of many technical requirements, such as the storage of topsoils, materials, and water, the establishment of nurseries, and the setting up of an ecological engineering capable of contributing to the transformation of the site. Its evolving character makes of the edge area a living and inhabited landscape.