The Paris Catacombs, France
This gorgeous city sits above over 200 miles of mining tunnels dating back to the 13th century. While most of the tunnels beneath the city are just that; tunnels, a lot of them are also ossuaries, lined to the ceiling with bones. Back in the late 1700’s, when the cemeteries were getting too crowded and tunnels were collapsing, they decided to kill two birds with one stone and move the bones from the cemetery to reinforce the tunnel walls, and bury the fresh dead in the cemeteries. Over 7 million bodies were moved into the catacombs, some as old as 1,200 years.
As well, since there are so many tunnels beneath the city, you can also find old war bunkers, guerrilla bars, cinemas and the occasional person who’s made their home.