from the Independent UK:
Cataphiles are Parisian urban explorers who illegally wander the Catacombs, a term popularly used to describe a vast network of underground galleries, tunnels and crypts under Paris. Originally built after the French Revolution to house the remains of destroyed tombs during the expansion of the city, the Catacombs are testimony to over two centuries of the city's historical heritage. For example, they were used as shelters by the French resistance during the Nazi occupation of Paris in the Second World War.
Beginning in the late Sixties, Parisians known as Cataphiles began restoring some of these spaces, and organising ossuaries to make way for more innovative creative spaces or themed neighbourhoods.
The Catacombs (or les k'tas as they are known locally) were formerly a network of stone mines. Nearly 80 yards below the city's cobblestones, there are no lights, electricity or even sound. There are no living creatures or fantastic urban legends in the Catacombs; however, it is estimated that as many as 300 Parisians visit the Catacombs weekly, entering via secret entrances throughout the city. Visiting them is illegal and considered trespassing, although it is mostly tolerated by locals. If caught, trespassers face a small fine.
A small portion of the Catacombs is open to the public or tourists. Entrance to the official Catacombs is restricted, though, and only consists of a tiny part of an extensive network of underground tunnels which spans more than 300km (about 186 miles) in length.
Some passages can be very low, narrow, or partially flooded. Because of these dangers, accessing the other parts of the Catacombs has been illegal since 2 November, 1955. ...........(more)
The complete piece is at:
http://www.independent.co.uk/news/world/europe/going-underground-exploring-the-paris-catacombs-2117011.html