UNESCO (United Nations for Educations, Science and Culture Organization) launch a rehabilitation operation of its site welcoming permanent delegations of the institution in the XV arrondissement of Paris. The renovations mainly aim at restoring building V, conceived by the architect Bernard Zehrfuss and the engineer Jean Prouvé between 1966 and 1969, as well as the gardens designed by André de Vilmorin. Landscaping is realized according to the simple and rigorous architectural writing that highlight the prestigious nature of the organization. First of all, the constraints of car access and pedestrian circulation have been fully reconsidered. The entrance esplanade is designed as a unitary granite base, a typically Parisian floor. The existing trees are reinforced by new plantations bringing a more forested character while the lawns are replaced by ferns. Lawns are replaced by a set of ferns to recall an undergrowth landscape. Through these transformations we propose a more interesting ecologic environment but also that needs less maintenance. This new place of life intended for the employees of the institution is conceived as a micro clearing in which tables and mobile chairs at disposal allow the appropriation of the garden. The four patios of the main building function as skylights for the offices. Each patio recalls a miniaturize natural landscape: naturalists gardens densely planted. The project includes the installation of thermophilic grasslands on the rooftops. These grasslands help to reduce the urban heat island and allow for a virtuous management of rainwater. Lightly vegetated, they require little maintenance and are adapted to structural constraints and sunlight conditions.