Nestled in the heart of the citadel of Bonifacio, in the southern French island of Corsica, this daycare is part of the former Montaur military district. Amid stone towers, the educational facilities rise with a concrete material that incorporates aggregates of the site, using lime as binder. This lime concrete has a rough texture and a color reminiscent of the geological stratification of the limestone cliff. The horizontal beds of rammed concrete and the roofs of Genoa slate fuse the building with the surroundings. Elementary and ancestral techniques and features were brought back, such as the spatial configuration around a square-shaped interior courtyard, the material quality, the thickness of the facade, and the building inertia, which makes it possible to cool air without consuming much energy.