Ouvrage Sapey is a work (gros ouvrage) of the Maginot Line's Alpine extension, the Alpine Line, also known as the Little Maginot Line. The ouvrage consists of one entry block, three artillery blocks and one observation block two kilometers west of Modane. The ouvrage was built beneath the older Fort du Sapey. The new work cost 12.8 million francs. The ouvrage and fort were accessed by an aerial tram built in 1908, which also connected to Fort du Replaton, located down the slope from Sapey.