The catacombs are the number one reason I would visit Paris. Very interesting and a lot of history.
I've heard that people have actually gotten lost down there and never recovered.
Blurb from this site:
http://members.aol.com/_ht_a/plinhardt/LINHARDT_Paul/catacomb.htm"In 1785, the city officials decided to use the quarries as burial grounds. The bones of some six million skeletons were moved there from overcrowded cemeteries considered to be health hazards. Among their ranks were the rattled bones of Rabelais, Pascal, Montesquieu, and the Mansard Brothers. The ossuary workers had a bizarre artistic temperament. They amused themselves by stacking the bones in macabre skull-and crossbones arrangements. Technically, the term "Catacombs" refers to the 11,000 square meters of ossuary known as the Empire of the Dead. However, in the folklore of the people, all 300 kilometers of tunnels from the original quarries also carry the appellation "The Catacombs of Paris".