Paris’ most macabre sight are these skull- and bone-lined underground tunnels. In 1785 it was decided to rectify the hygiene problems of Paris’ overflowing cemeteries by exhuming the bones and storing them in disused quarry tunnels, and the Catacombes were created in 1810. After descending 20m (via 131 narrow, dizzying spiral steps), you follow dark, subterranean passages to the ossuary (about 1.5km in all). Exit up 112 steps via a 'transition space' with gift shop onto 21bis av René Coty, 14e.
The route through the Catacombes begins at the 2018-opened entrance on av du Colonel Henri Rol-Tanguy.
The surface is uneven and can be slippery – sturdy shoes are essential. In the tunnels the temperature is a cool 14°C. Flash photography isn't permitted. It's not suitable for young children or anyone faint-hearted.
Online bookings are pricier but include an audioguide and guarantee a timeslot, whereas standing in the queue does not, as online ticket holders have priority.
Bag searches are carried out to prevent visitors 'souveniring' bones.