Grottes de Mandrin

In reality, these caves, built by the army in 1843/1844, are much more recent and have no connection with Mandrin.

The site was first used as a stone quarry during construction of the Bastille fort. Then the Military Engineers realized that caves dug here could complete the defensive system, offering defenders the possibility of catching the enemy from the rear, should he attempt to attack the keep and advance onto the glacis.

Caves were therefore dug, partly using dynamite, and laid out so as to face the glacis. To link them to the Bastille fort, an underground passage was cut through the mountain to allow soldiers to move around without being seen by the enemy. From the caves, the 80-step underground passageway leads to a path that ends near the fort's gate.

The underground is open to the public, who particularly appreciate its coolness in summer.