Built between 1891 and 1893, Fort de Lenlon is an infantry fort at an altitude of 2,510m. Semicircular in shape, it is nicknamed the "Boyard of the mountains".
Fort de Lenlon was built on the ridge overlooking Fort de l'Olive below.
Consisting of a first floor and a first floor, the fort could accommodate 40 men on each floor. Spread over the two levels, the fort's defense was ensured by the 48 gun battlements built into the thickness of the masonry. The fort had no other armaments.