The Catacombs in Paris conceal numerous dark secrets. There is something inherently bone-chilling about the ossuaries — and many people consider them the most taboo and creepiest place in the world.

In a city that is popularly known for its romance, love of desserts, and fashion — the Catacombs are not considered to be the most prominent landmark in Paris, but it is surely the spookiest. It seems that the catacombs are hiding a ghastly secret underneath the city. Here are some little-known and creepy facts about the expansive Catacombs that will startle you.

Clandestine operations were conducted in the Catacombs by secret groups.

During a police training exercise in 2004, the trainees stumbled upon a secluded area in the Catacombs and found a massive cinema room featuring a giant screen, other equipment, and a restaurant facilitated by power lines and installed phones. A secret camera was capturing photos of the police officers as they walked past the entrance. The people still do not know who owned that underground facility.

The Catacombs provide shelter to more than six million deceased Parisians.

During the 18th century, the cemeteries in Paris were running short of space. All bodies could not be buried properly - resulting in the spread of various diseases. The Parisian officials ultimately decided to move the bodies to the underground quarries in the city. They accommodated over six million bodies in the Catacombs from the 1780s to 1814. The deceased people were transported to their final resting place via carts.

Farmers started growing mushrooms in the Catacombs

During the 19th century, a man named Monsieur Chambery went down and noticed wild mushrooms growing in a patch within a chamber. He made up his mind to use the deserted underground tunnels for cultivating button mushrooms. This practice was soon approved by the city’s Horticultural Society, and farmers flocked down immediately to cultivate mushrooms.

The tunnels were used during World War II by both parties.

The existence of the Parisian tunnels was known to everyone by the time of World War II, and also the fact that they spread over several miles underground. The French Resistance used the tunnel system of the Catacombs to plan attacks and hide during the war from the Germans. Similarly, the Nazis were also using the abandoned tunnels to build bunkers.

Bones arranged in “Decorative” structures and patterns

During the 1780s, the bones were placed ordinarily in the tunnels, but later the workers started arranging the old bones into decorative structures, like circles and in the shape of a Barrel. They look like a circular pillar surrounded by tibiae and skulls, offering support to the roof. Indeed, a very morbid decoration.

If you are in Paris and have already visited the Eiffel Tower and other prominent tourist attractions, it is time to head to the Catacombs.