The Catacombs of Paris
There are more than 7 million people buried in this 178-kilometer underground tunnel. These bones are arranged along the wall and are signed with the time of death. The air is dry and full of the smell of decaying bodies. The Catacombs first served as a limestone quarry and then because cemeteries were overwhelmed and disease broke out, it was used to bury people since the 1770s.
The underground cemetery became a tourist attraction on a small scale from the early 19th century and has been open to the public on a regular basis since 1867.