Halloween in Paris: 5 Places That Will Give You Chills

About 20 meters under the city, the bones of more than six million Parisians line the galleries of old limestone quarries. They were moved here from 1785, when the city's overflowing cemeteries became a health hazard; among them was the Cemetery of the Holy Innocents, whose Renaissance fountain still stands in Les Halles. In 1810 and 1811, the quarry inspector Héricart de Thury arranged the bones into the neat walls of skulls and femurs you see today. Visitors go down 130 steps into a constant 14 °C, so bring a jacket. At the door of the ossuary, an inscription gives the warning: “Stop! This is the empire of death.”

Hidden inside a working police station, this little-known museum was imagined in 1909 by the prefect Louis Lépine, using objects gathered for the 1900 World's Fair. It traces more than four centuries of crime and policing in Paris. Among its exhibits are a guillotine, prison cell doors and objects from famous criminal investigations, along with a room on Alphonse Bertillon, the pioneer of criminal identification. It is free, rarely crowded and quietly unsettling.

Behind this iron gate near Pigalle lies a private lane, closed to the public, lined with 19th-century houses where Alexandre Dumas, Toulouse-Lautrec and Django Reinhardt once lived. The darkest reputation belongs to the neo-Gothic house at number 1. According to the legend, the composer Victor Massé died paralysed there in 1884, another occupant died of the same illness a century later, and a maid was beaten to death on the stairs; her ghost is said to haunt the house. You can only look through the gate from the street, which perhaps makes it even more mysterious.

Inside the Hôpital Saint-Louis, founded under Henri IV in 1607 to isolate plague victims, a hushed museum holds nearly 4,800 hyper-realistic wax casts of skin diseases. In 1867, Dr Lailler asked the sculptor Jules Baretta to reproduce patients' faces and limbs in wax, so that doctors could be trained before colour photography existed. The method continued until 1958, and the museum building was inaugurated in 1889. Displayed in old wooden cases, these casts are fascinating and deeply disturbing. Not for the faint-hearted.