Ouvrage Croupe du Réservoir is a lesser work (petit ouvrage) of the Maginot Line's Alpine extension, the Alpine Line. Located on the heights of Roquebrune at an elevation of 139 meters, the ouvrage consists of one entry block and one observation block facing Italy and covering the Grande Corniche road. The fortification was manned by 60 troops of the 58th Demi-Brigade Alpin de Forteresse (DBAF) under the command of sous-lieutenant Roman.