Ouvrage Plan Caval

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.

The ouvrage consists of three blocks facing Italy at an altitude of 1,870 metres (6,140 ft). The ouvrage was manned by 287 soldiers in 1940, under the command of Captain Philipp. Plan-Caval was located to control the Maglia and Cayros valleys, as well as providing flanking cover the La Béole and Saint-Véran. An extensive set of underground barracks and magazines near the uncompleted entrances was never started, so that the ouvrage as constructed consists mostly of a single narrow gallery connecting the combat blocks.