In Cormeilles-en-Parisis, behind a large wooden gate and tree-covered embankments, lies one of the best-preserved military forts in Île-de-France. Built after the War of 1870 to defend Paris, the site is open to visitors only during guided tours held on the first Sunday of the month. The 1.5-hour tour takes visitors through its underground passages, powder magazine, and former artillery positions.
Fort de Cormeilles, a military fortification built to defend Paris
The defeat at the hands of Prussia in 1870 had exposed the weaknesses of Paris’s defenses. A few years later, General Raymond Séré de Rivières therefore initiated the construction of a new ring of forts, located farther from the capital than Thiers’s fortifications. The Cormeilles fort was built between 1874 and 1877 on the heights of the Val-d’Oise, with the mission of monitoring the Argenteuil plain and the area around the confluence of the Seine and the Oise.
The construction project was far from simple: since stones, bricks, and cobblestones were difficult to transport up to the hill, a specially built railroad connected the site to the Seine. Three years and 3.3 million francs later, the fort was completed. It subsequently served as a model for other military structures in the region.
Much of the complex is hidden beneath thick layers of earth, designed to absorb enemy fire. This is also why the fort goes almost unnoticed from the outside. You have to pass through the entrance and walk between the walls to grasp its true scale. During the tour, you’ll go up to the cavalier, where the artillery took position, then into the powder magazine, the gun shelter, and the double caponier tasked with defending the moats.
Several small museums complement the tour with uniforms, military equipment, and objects related to the soldiers’ daily lives. The fort has also served as a filming location for various productions, including OSS 117!
The tour ends with a rather unexpected treat: the “Pavé du Fort, ” prepared by a local artisan from Cormeilles and then baked in the old ovens of the military bakery. Sales begin at 4:00 p.m. during several monthly open houses, even for those not taking the tour. No individual reservation is required to enter the fort, but it’s best to arrive before the gates close, shortly after 3:00 p.m.
📍Location: Fort de Cormeilles – 1 Rte Stratégique, 95240 Cormeilles-en-Parisis