I've been to the Catacombs. Really freaky, because the builders left all kinds of morbid poetry carved into the stone columns and supports to remind visitors of their own mortality. (Makes me sorry I learned how to read medieval French.) They also did things like make hearts and crosses and other patterns out of human skulls in the walls. Maybe I'll find and upload our photos.
For some background, the Catacombs were built in the late middle ages as part of a vast urban renewal program in Paris. Essentially the government demolished all the old, rotting, plague-infested, fire-hazardous tenements of the poor and built new sturdy masonry buildings and wide, straight tree-lined boulevards. Part of this involved digging up countless medieval cemetaries, so the Catacombs were built to house the remains of all the skeletons they dug up, since they posed a significant health risk.
The catacombs were widely used by the rebels in the French Revolution, the resistance during the Nazi occupation, and were home to the gypsies in Victor Hugo's The Hunchback of Notre Dame. They were opened in the 19th century, along with the sewers (les egouts) for tourism. I never knew they had a club/restaurant down there, though.
