Fort du Salbert Entrance

Fort du Salbert, also known as Fort Lefebvre, was built between 1874 and 1877. It was named after General François Joseph Lefebvre. It forms part of the Séré de Rivières system fortifications in the fortified region of Belfort in northeastern France. It is located at the summit of Salbert hill to the northwest of Belfort. During the early years of the Cold War it briefly served as an air defense coordination center. -from Wikipedia