Delve deep below the city of Paris for a small-group tour of its catacombs, home to the exposed remains of approximately 6 million people. Join your guide wandering the dark, damp tunnels of this subterranean tomb and discovering its fascinating history. You'll learn how they were once a series of limestone quarries and served as a secret hideout for resistance fighters during various wars. And who knows? Maybe you'll even encounter a ghost or two.