Loving life in Paris' Empire of the Dead

Paris, France (CNN) -- Beneath the streets of the City of Light lies a world draped in darkness and shrouded in silence. The tunnels are narrow, the ceilings are low and death is on display.

The skulls and bones lining the walls, arranged in a macabre fashion, make up what is known as the Empire of the Dead -- the Catacombs of Paris.

The catacombs snake below the city, a 321-kilometer (200-mile) network of old quarries, caves and tunnels.

Some Parisians are drawn to this largely uncharted territory -- a hidden network of adventure, discovery and even relaxation. They are known as 'cataphiles' and the catacombs are their playground.

It is a top-secret group. Catacomb entrances are known only to those daring enough to roam the networks on their own -- and break the law.

Entering unauthorized sections of the catacombs is illegal and a police force is tasked with patrolling the tunnels, and caught cataphiles risk fines of up to 60 euros ($73).

But for explorers like Loic Antoine-Gambeaud and his friends, it is a risk they are willing to take.

"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," Antoine-Gambeaud said.