The Fort des Trois Têtes, named after the rocky plateau on which it extends, is the most important work of the fortified barrier built by Vauban in the 18th century to prevent enemies from taking positions above Briançon in the Hautes-Alpes department. It was built from a first entrenched camp established on this height in 1709. Work began after the signing of the Treaty of Utrecht in 1713, which modified the border with the Duchy of Savoy, and ended in 1734. The Fort des Trois Têtes opposes 1,968 ft (600 m) of front to the enemy over a depth of 1,148 ft (350 m).