Ouvrage Plan Caval, Military fortification in Breil-sur-Roya, France

Ouvrage Plan Caval is a military fortification in the Maritime Alps. The structure consists of three combat blocks connected by an underground passage, sitting at an elevation of about 1,870 meters.

Construction began in the late 1930s as an extension of the Maginot Line into the Alps, designed to face Italian forces. By 1940, it housed roughly 287 soldiers under Captain Philipp's command.

The fortification represents French military engineering expertise through its integration into the mountainous landscape of the Maritime Alps defensive sector.

The site sits at significant elevation and requires proper gear and reasonable fitness to reach. The underground passages are cool and dark, so bringing a flashlight is helpful.

The three completed blocks were cast in summer 1938 under reduced "protection no. 2" concrete, before the full design was approved. Block 3 was concreted in summer 1939 but never received its 81 mm mortar turret, and its gallery connection was sealed off.