The drawbridged entrance to this huge subterranean sits at the top of Ste-Agnès village. The 2500-sq-metre defence was built between 1932 and 1938 as part of the 240km-long Maginot line, a series of fortifications intended to give France time to mobilise its army if attacked. The fort was maintained throughout the Cold War as a nuclear fallout shelter and the army only moved out in 1990.
Interestingly, it is thanks to this active military history that the village of Ste-Agnès is so picturesque today: all new developments were prohibited in the village during the army's presence, a measure that the village has since maintained.
