If you know much about European history, you are aware that a lot of people have died in Paris. A lot. So much that eventually they ran out of room to bury people. To rectify this problem, someone had the great idea to dig up a bunch of the dead people and put their bones in a network of tunnels underneath the city. The designer surely must have been an artist as it was decided that all the bones would be put into decorative patterns and displays. He also must have been a businessman because the catacombs quickly became a paid travel destination. I learned about these around a year ago and ever since I have been absolutely stoked to go see them. Last week I finally entered the passages and it was out of control. I highly recommend trying this out if you ever are near Paris.