The entrance for tours to the Paris Catacombs is located just across the street from the Denfert Rochereau Metro station. The Catacombs, are in fact only a small part of what were originally the quarries for Paris, that were formed during the quarrying the stone from which the grand buildings of Paris were constructed. It is here where the bones of generations of Parisians have been stored in order to solve the problem of overcrowding in the cemeteries.
Entrance to the catacombs is through a plain black door in a small building that can be easily missed while walking by it. On entering you will pass a notice (mostly ignored by visiting tourists) which states that flash photography is strictly forbidden. After descended a long spiral staircase, you will enter a small gallery displaying drawings, photographs. On leaving the gallery, you will enter the dark and damp area of the tunnels themselves. Along the way, there are signs stating when that particular area had been excavated.
There is no definitive map of the underground quarries, but it is estimated that there is about 300 kilometres of galleries, under the 5th, 6th, 8th, 12th, 13th, 14th, 15th, 16th and 20th districts. with the most extensive part of the labyrinth being located under the 5th, 6th and 14th districts, and is thought to be about one hundred kilometres in length.
Some areas of the Catacomb walls are covered in graffiti dating from the 18th century. There is evidence that during the 19th century, families actually lived in the catacombs. In 1871 a group of monarchists were killed by communards in one of the chambers. During World War II, members of the French Resistance used the system of tunnels to hide out in, while at the same time in another part, German soldiers constructed an underground bunker (not part of the catacombs tour). Unofficial visits to the underground quarries of Paris are not permitted, especially as some areas can be very dangerous. However, secret entrances are scattered throughout Paris, accessed through the sewers or metro tunnels. There are also a number of manholes that lead into the catacombs.
The bones began accumulating in the catacombs in 1786, just as momentum for the Revolution was building in Paris. Land was becoming increasingly scarce and at the same time the cemeteries were becoming overcrowded. So the government of the time made the decision to move the remains of the dead to the empty limestone quarries, so freeing up the land presently being used as cemeteries for other use. While moving the remains from the cemeteries, no attempt was made to identify or separate individual bodies, but the bones were marked with a plaque specifying the cemetery they came from and the year when they were moved. The work was completed in 1860, by which time an an estimated five to six million skeletons had been relocated.