The Gros Ouvrage of Sainte-Agnès is part of the Alpine extension of the Maginot Line and was built between 1932 and 1938. It is at 780 metres above sea level and is near the site of a much earlier (16th century) fortification. The Maginot fort has one entry block, two artillery blocks, two infantry blocks and one observation block.
Inside the fittings are in remarkably good order (mostly origianl but some period replacements). These include well preserved support facilities including generators, air-filtration plant, kitchen, dormitories and sick bay. Block 2 is one of the largest on the entire Maginot Line and its armaments include one machine gun turret, one grenade launcher, one twin machine gun port, two 75mm gun ports and two 81mm mortar ports. It also had the ability to signal optically with neighbouring forts.
In 1940 the fort fired around 1,500 rounds against advancing Italian troops. The fort was retained by the French Army until the end of the Cold War in case it was needed as a nuclear shelter or command post. In 1990 it was handed over to the local community who now open the well-equipped fort on a regular basis