While the Catacombs proper comprise a small portion of the tunnel and mine network under the city, small is a relative term. At one hundred and eighty six miles of tunnel length, the Paris Catacombs – or as it is officially known, the “l'Ossuaire Municipal” or “Catacombes officiels” is the world’s largest grave. What the Catacombs are, is a large underground ossuary, which is a place designed to serve as a final resting place for human remains. The Catacombs were opened in response to two separate but simultaneous crises in the city of Paris in 1774. At that time, the city first had a lack of space to bury the dead; and second, had a number of cave-ins and collapses in the mine and tunnel network. The Catacombs were devised as a solution to address the tunnel instability problem, and as a place to store the city’s many dead. From 1774 onward, over six million bodies were moved into the Catacombs from the city’s old cemeteries. If an ancient underground tunnel and mine system that has over six million bodies in it wasn’t interesting enough, it is also worth noting that tours of the Catacombs have been going on since 1814.