Denfert-Rochereau Ossuary (Paris, France)

Also known as the “Catacombs”: “Far below the city streets of Paris, in the quiet, damp darkness, seven million Parisians lie motionless. Their skeletons, long since dis-interred from the churchyard graves their survivors left them in, are neatly stacked and aligned to form the walls of nearly one kilometer of walking passage.”