LOS ANGELES, CA (Catholic Online) - Below the City of Light's 12 million residents lay the remains of 6 million others, also known as France's Empire of the Dead. The catacombs are the subject of a new documentary on CNN.

A 200-mile network of old caves, tunnels and quarries, it is a powerful draw for a hardcore group of explorers with a thirst for adventure. The official "tourist-friendly," legal entrance can be found off Place Denfert-Rochereau in the 14th arrondissement of Paris, near the Montparnasse district.

Tourists descend into the city's dark and dank bowels for a whistle-stop tour of a small section of the catacombs.

"I think people are fascinated with death. They don't know what it's about and you see all these bones stacked up, and the people that have come before us, and it's fascinating. We're trying to find our past and it's crazy and gruesome and fun all at the same time," an interview subject on the CNN documentary says.

Many other Parisians like to go further and deeper to explore the network of winding tunnels and human remains. Those who enter the cave network illegally and unsupervised have been termed as "Cataphiles." These clandestine groups go deep underground, using hidden entrances all over the city, staying for days at a time, equipped with head lamps and home-made maps.

Street names are helpfully etched into the walls to help explorers navigate their way around the underground version of the city. Some hardcore groups have even been known to throw parties in the tunnels and happily imbibe.

The silence experienced deep in tunnels cannot be replicated anywhere else, Cataphiles claim.

"I think it's in the collective imagination. Everybody knows that there is something below Paris; that something goes on that's mysterious. But I don't think many people have even an idea of what the underground is like," Urban explorer Loic Antoine-Gambeaud tells CNN.

Those caught wandering about unauthorized may have a price to pay. Police tasked with patrolling the tunnels have the power to hand out fines of 60 euros to anyone caught walking around unsupervised.

The catacombs were subterranean quarries which were established as limestone was extracted deep underground to build the city above. It wasn't until the 18th century that the catacombs became known as the "Empire of the Dead" when they became the solution to overcrowding in the city's cemeteries.

Human remains were transferred to the underground quarries in the early 1780s. The space was the perfect solution to ease overcrowding in cemeteries. 

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