Petit ouvrage du Plan Caval - 6 blocs (3 blocs completed) - Located 4,5 km East of the Col de Turini - Access from the named pass. At the Col de Turini take the D68 to Authion. Continue on this road until you see the ruins of barracks on your right. Currently abandoned.

Commandant: Cne Philipp Regiments: 40th DBAF & 158th RAP Generators: Not Installed Troops: 11 Officers & 287Men.

Plan Caval is an unfinished Gros ouvrage with 6 blocks planned but only three built. These blocks were never finished and the fort was never armed. Block 4 is partially camouflaged as it's is clad in stone. It would have been only lightly armed with no heavy guns or mortars. A ladder alongside the lift shaft gives access to the corridor 20 feet below. Although the lift shaft with its gate has been constructed the lift and its associated machinery have never been installed. The passage is concrete lined and very clean. It is necessary to watch the floor carefully as there are a number of uncovered drains. After a short distance there is a crossroads, to the left is a collapsed or backfilled shaft to the surface and to the right a short passage leads to Blocks 5 & 6.

There is a long tunnel straight ahead with a dog leg and a defensive embrasure in a room to one side. The passage continues for about 75 yards eventually opening out into a series of unlined tunnels running left and right. A number of these have wooden pit props and one of them is very heavily propped with vertical supports and cross timbers. A number of passages have collapsed but it's possible to climb over these collapses to reach a series of very high parallel tunnels, the possible location of the proposed caserne and usine areas. From here there was a tunnel to a blocked door, presumably the original planned entrance to Plan Caval. This was later located on the surface on a valley floor below the road.

Having looked at the underground features we explored the surface. There is a Maginot block in the middle of the ruined barrack blocks but the turret and cloche were never fitted and the holes for them were later filled with concrete. There is a trench system on top of the hill with two small machine gun positions.

It was fascinating to see the various phases of construction of a Maginot Line Fort. It is unclear why work on this fort started so late but it is recorded that construction stopped in 1940 because of the war.