The official name for the what is better known as the catacombs is ‘les carriers de Paris’ (the quarries of Paris). They are underground tunnels what were lime stone quarries in the roman era, and in the late 18th century they were turned into mass graves. This was ordered by Monsieur Thiroux de Crosne who at the time was a Lt General of Police and by an inspector of the quarries Monsieur Guillaumot. It was decided mainly because the district Les Halles was suffering from the spread of disease due to contamination which was being caused by improper burials and mass graves. So it was decided to remove the bones and to place them in the disused quarries. Among the first to be removed were those from the Saint Nicholas des Champs cemetery.

Due to the problems caused by the amount of underground tunnels and the possible threat of them caving in, in 1777 the Inspection generale des Carrieres (General inspection of the quarries) was established by the government to monitor the quarries. This still continues today as now there are not just the catacombs but also subways, railway tunnels and sewers to be taken into consideration as well.

You are allowed to visit the catacombs on official visits, these tours are only a small part of what is a vast network of underground tunnels, it is illegal though to enter without an official guide and as been since 1955, and a fine will be enforced if you are caught.

The catacombs are said to be haunted, and even in the light are not a place for the faint hearted, it is said that there a few ghosts that still roam the tunnels and sometimes blue mists can be seen swirling around.