Paris Catacombs: The Underground Empire of the Dead

The Paris Catacombs are one of the world's most extraordinary visitor experiences — a network of 300km of tunnels beneath the city containing the remains of approximately 6 million Parisians, arranged in the decorative ossuary style that has made this subterranean city of the dead one of Paris's most haunting and unforgettable attractions. The tunnels were originally limestone quarries that provided the stone for Notre-Dame and the Louvre; by the late 18th century, overcrowded Parisian cemeteries were contaminating the water supply, and the bones were transferred to the tunnels in elaborate nocturnal processions over 12 years. The visitor section — 2km of the full 300km network — includes the ossuary itself, where skulls and femurs have been arranged in decorative patterns and walls by the transferring priest Héricart de Thury. The full network of "unauthorized" catacombs beneath the city is illegally explored by cataphiles — Parisian urban explorers — but the official entrance on Place Denfert-Rochereau is the only legal access. Book tickets online (they sell out weeks ahead); guided skip-the-line tours are worthwhile for historical context. The site maintains a steady 14°C year-round — bring a layer.