Millions of skeletons
1 place Denfert-Rocnereau, 14e. A macabre tourist attraction laid out in abandoned Gallo-Roman stone quarries, this is no ancient Roman necropolis, but an 18th-19thC cemetery clearance operation. Around six million skeletons line the 300 km of tunnels. A short but eerie section has been open to the public since 1874.