A spiral staircase in the Denfert-Rochereau section of the catacombs (all photographs by the author unless indicated)

Perhaps the most well-known “ruin” in Paris is the catacombs, a network of quarries that span around 200 miles under the city (in fact Parisians have been known to compare their city to a holey cheese there are so many tunnels dug out under the surface).

A small portion of the catacombs were renovated and turned into ossuaries when the original resting places for the bodies were no longer viable, giving it the reputation of being one of the world’s largest graves.

Since 1874, a section has been open on a regular basis for tourists. However, what a lot of tourists don’t realize is that this is only a small segment of the mass network of tunnels.

Upon entering the ossuaries, you are faced with this warning: “Arrête! C’est ici l’empire de la Mort” (“Stop! Here lies the Empire of Death”), whereupon you are met with the first of the remains of the six million people that are buried within the catacombs.

Le Carrefour des Morts (“The Crossroad of Death”), a part of the catacombs not open to the public (photograph by Adam Slater)

As a popular tourist attraction, the catacombs now often have an enormous queue snaking around the block, thus it is always advisable to be early and expect a wait, and dress in layers — it can be extremely cold or hot outside, but the catacombs maintain a fairly consistent temperature once you enter the quarry tunnels.

For the more daring, the museum is only the start of your potential journey. The tunnels extend far beyond what is available to see here, but nonetheless provides a fascinating visit. Though you might just find yourself bending the parameters of “easily accessible” and joining the cataphiles in order to seek out the rest.

Read on via The 10 Most Accessible Ruins in Paris | Atlas Obscura.