The Fort de Tournoux is constructed more-or-less continuously up the side of the mountain from altitude to in several levels. The lowest level is the barracks (Caserne Pellegrin) at 1300m next to the main road from the Cols (Larche and Vars) to the village of la Condamine and the towns of Jausiers and Barcelonnette. A battery at this level, built between 1846 and 1862, is called Batterie XII. Linking these with the Fort Moyen ("middle fort", also known as Fort Grouchy) is a road, constructed to allow mules to ascend with carts – so at a maximum gradient of 10% with frequent hairpin turns. The hairpins were constructed so that the mules could park their double-ended carts and run-around to pull the cart in the opposite direction up the next stretch, thus avoiding the need to turn around the hairpin bends, which often caused carts to topple over and spill their contents.