The works consist of energy efficiency upgrades, structural renovation, along with the total restyling of a residential building from the Sixties, which can be divided into three independent apartments. The project acknowledges the impressive volume of the preexisting building and emphasizes it by removing its overhangs, simplifying its geometry, redesigning solids and voids with large squared holes, and transforming the roof into a private, useful floor area. The massive presence of the building, due to structural reinforcement and energy-saving insulation, gives it a fortress-like appearance, which is further enhanced by the rough interior wall finishes in continuity with the exterior. Its severe relationship to the ground is emphasized by a large rock, on which the building is sited, and a play of voids and double heights on the southern side renders the rock visible from all floors. The severe atmosphere created by straight lines is softened by custom-made furnishing, wooden doors and windows, as well as large views of the green forest and light cuts intercepting the different levels of the building. In order to fulfill the requirements of flexibility imposed by today’s dynamic society, the building can be divided into three units: three apartments, three entrances, three finishing textures on the façade. All the apartments can be connected through the elevator and the interior stairwell, whereas the external metal stairs make the apartments and the rooftop independently accessible.