Underground Citadel of Verdun

After the Franco-Prussian War in 1970, a 7-kilometer network of tunnels was dug under the 17th-century Verdun Fortress, which served as a bunker, command base and warehouses. Today it houses a museum dedicated to the history of World War I and the Battle of Verdun. Visitors watch the exhibition located in the tunnels while traveling on a special train.