Catacombes de Paris 130 steps to go down and 83 steps back up to street level. Tickets go on sale on site only, no online booking available. Open daily from 10am to 8pm, except Mondays and public holidays. Last admission: 7pm. 10€.
http://www.flickr.com/photos/albany_tim/ / CC BY 2.0 For urban explorers, few places are more coveted than the Catacombs of Paris. Long sealed off to the public, these harrowing subterranean chambers house an 18th century cemetery – essentially an anonymous mass grave. Beyond this, a labyrinth of tunnels extends for 280km beneath Paris in a network of disused stone mines and galleries.