Fort de Tournoux Parc National Du Mercantour

Originally built to protect the French border from invasion, and later used as part of the Maginot Line during WWII, this hillside fortress 18km northeast of Barcelonnette provides an evocative reminder of just how close you are to the French frontier here. Guided visits explore the fortifications, including gun batteries, casements and dugouts. There are several more military ruins to visit around the valley. The fort is reached via a perilously steep, twisting mountain road.