Conversion of an office space into a spa of 1500 square meters in the district of La Part-Dieu in Lyon. The Poseidon’s spa was inspired by the different layers of the ocean (the abyssopelagic zone, the Bathypelagic zone and the Mesopelagic zone) to immerse the visitor into the universe of the Greek god. Therefore, the luminosity of spaces varies from the darkest (ground floor) to the lightest (second floor). All is built around a circular staircase crossing the entire different floor. On the top of it, a glass dome is overhanging the structure. The infrastructure includes a spa, a shop, a hotel and a restaurant.