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In the late eighteenth century, health concerns led the city of Paris to empty all the cemeteries within city bounds and move the remains to a series of catacombs outside the walls. There are an estimated six million people down there — you see only a fraction of the remains on your tour — and most of it is very difficult to photograph, as they don’t allow tripods or flash (so as to protect the bones). This picture, however, came out splendidly.