This stunning capture of the underground galleries at Fort de Roppe near Belfort, France, has featured as one of Wikimedia Commons’ pictures of the day. Built between 1875 and 1877, the fort stands near the summit of a hill near the town of Roppe, and is part of a ring of fortifications around the city of Belfort to the south. The underground galleries were built during the First World War to connect the fort to outer gun turrets and the concrete troop shelter.
During World War Two, the heavily fortified underground galleries and tunnels enabled 400 French troops to hold out for three days before surrendering at the close of the Battle of France. Now abandoned, the galleries at Fort de Roppe are in good condition but public access is prohibited. The fortified region, including the Belfort Lion, also featured in this earlier article.