Ouvrage Col du Granon, Alpine Line fortification in Val-des-Prés, France

Ouvrage Col du Granon is a small infantry work of the Alpine Line at 2,329 m, about 300 m north-east of the col of the same name in Val-des-Prés. Of the four planned blocks only three were built: the entry block B1, the infantry casemate B3 and the GFM cloche block B4, linked by an underground gallery with raw concrete walls and barrel-vaulted ceilings. Block 2 was never poured, though its excavation trench is still visible. The concrete is 1.40 m thick, proof against 150 mm shells.

The CORF studied a mixed-artillery project in 1931, reduced in 1933 to a small infantry ouvrage; work was interrupted from 1935 to 1937. Only entry block B1 existed in early 1939, when the 82nd BAF Alpine troops began blocks 3 and 4; block 2 was never poured. The garrison took up permanent duty in April 1939, replacing a ski-scout section of the 159th RIA. The ouvrage was untouched in June 1940 and its weapons returned to the Guillestre arsenal after the armistice.

The fortification reflects French military engineering of the 1930s through its network of underground galleries connecting different defensive positions and observation points across the mountainside.

The ouvrage is maintained and kept closed by the army, entrusted to the chasseurs alpins; there is no access inside, so the blocks and the excavated site of the unbuilt Block 2 are seen from outside. It stands at 2,329 m, about 300 m north-east of the Col du Granon, above the Séré de Rivières barracks known as the Fort de Granon.

The annex block about 50 metres north-northwest of and slightly below the entrance, with a twin Reibel machine gun embrasure, is described in the sources as apparently the only one of its kind on the Maginot Line. The B2 artillery block was never poured, but its excavation trench is still visible in the ground.