Planned during General Haxo’s time, the Fort des Barres was not actually built until the eve of the 1870-1871 war, making it one of the last bastioned works built in France. Built from 1865 onwards, Fort des Barres has a fairly simple layout. It consists of two bastioned fronts, each 240 metres long. Two imposing traverses protect the interior of the fort. Each of them houses gunpowder magazines. A casemate was built into the central salient.

The fort was protected by a very hight rampart due to the terrain, and was equipped with a number of improvements linked to advances in artillery. The open-air cannons were placed on earthen cavaliers built above the curtain walls. After 1874, a new belt of forts was built around Belfort as part of the defensive system developed by Séré de Rivières. Fort des Barres found itself in the second line of defence, in the central core of the stronghold. As such, it remained in use and armed. In 1893, large barracks were built on the inner esplanade to house the artillery regiment. Used as barracks until the 1970s, the fort was acquired by the town of Belfort. The barracks are used by Rockhatry as rehearsal rooms for music groups.