Venture below the avenues and Metro tunnels of Paris and into the Catacombs, whose population of skeletons far outnumbers the living city above. This small-group tour includes Skip-the-Line Entry and lets you access parts of the Catacombs that are off-limits to individual visitors, so you get more out of your experience. Exclusive sights include the Sacellum Crypt, where bones were blessed before beginning their rest in the tunnels.