Ouvrage Sainte-Agnès, Underground military fortification in Sainte-Agnès, France.

Ouvrage Sainte-Agnès is an underground military fortification carved into the rock above the village of Sainte-Agnès in the French Alps. A network of tunnels connects combat blocks, gun positions and support rooms spread across several levels beneath the hillside.

Built between November 1931 and October 1934 by the contractor Borie for 16.8 million francs, the ouvrage was commanded in 1940 by Captain Panzani. During the June 1940 Italian offensive it fired 1,201 rounds from its 75 mm guns, 80 from 81 mm mortars and 234 from 135 mm guns, hitting coastal roads on 21 June and the Col du Razet the next day. It stayed in government hands until 1990, when it passed to the town of Sainte-Agnès.

The living quarters inside the ouvrage, including bunks, kitchens and washrooms, are still set up as they were when soldiers occupied them. Walking through these rooms gives a clear sense of what it meant to live and work deep inside a mountain.

The tunnels are narrow and the floors uneven, so sturdy footwear is a good idea before heading inside. Temperatures underground stay cool year-round, so bringing an extra layer of clothing is worth considering.

The site sits at 780 metres, not 760, on the western slope of the 766-metre hill above the village. Ten observation posts reported to Sainte-Agnès, among them Pic-de-Garuche, whose observation block had the only example of a VP cloche built by military labour rather than the CORF design teams.