The Catacombs of Paris, France
The Catacombs of Paris have a rich history. In the 17th century, Parisian cemeteries were overflowing, so the government decided to bury the bodies in catacombs under the city. These catacombs were originally created to dig limestone quarries in the 13th century. About a mile of the catacombs are open today for public tourism, but most of the area is off-limits.
There are rumors of subterranean people or parties – in 2004, a movie theater was discovered carved into the catacombs themselves, equipped with a full bar, lounge, and a PA system that broadcast guard dog noises!