This group of five forts built by Sardinian monarchs from 1817 to 1834 to guard the Mont-Cenis pass against a possible French invasion. Each fort is named after a member of the House of Savoie. Fort Marie-Christine marks the highest point of the fortifications. The most important work is Fort Victor-Emmanuel, depicted by a string of several storey buildings along the cliff's edge. On the left bank of the Arc, Fort Marie-Thérèse is linked to the complex by the Pont du Diable (Devil's Bridge).