Sous les Sours-Muets - Rue St Jacques.
Carved plate indicating location (rue Saint-Jacques, under the school for the mute and deaf)
Catacombs of Paris (off-limit area), about 20 meters (60 feet) underground, under Paris city center.
This is a part of the 200 Km network of ancient tunnels not opened to the public, but regularly visited by trespassing urban cavers called "cataphiles". See more information in the album description.