National Geographic History on Instagram: "The Cimetière des Innocents—Holy Innocents' Cemetery—in Paris had been in use for centuries when a flood in 1780 resulted in rotting bodies littering a neighboring property. Subsequently, all of the cemetary's remains were exhumed and moved to the tunnels beneath the city. Here are five facts about one of the world's largest ossuaries that houses the bones of millions of people. Discover more about the secret underground world of Paris at the link in bi