Ouvrage Plan Caval is a lesser work (petit ouvrage) of the Maginot Line's Alpine extension, the Alpine Line, also known as the Little Maginot Line. The ouvrage consists of two infantry blocks and one observation block facing Italy. The ouvrage is located on the heights of L'Authion, surrounded by older fortifications. Three additional blocks were planned to make it a gros ouvrage but were not built. Cost for the full ensemble was estimated at 23 million francs.