Restoring the Empire of Death

Beneath the glittering city of Paris, France, lies one of the spookiest sites on Earth. It’s a network of damp, narrow passageways lined floor-to-ceiling with human bones! These are the Paris catacombs—a massive underground tomb that holds the remains of more than 6 million people.

In the late 18th century, the graveyards of Paris were overflowing. Officials started stashing old bones in tunnels under the city, creating the catacombs. The site was an instant hit with tourists. Today it draws more than 600,000 visitors a year (see “Would You Rather . . . Spend the Night With Skeletons or Snakes?” in Science World, August 28, 2023). But all those tourists have caused a lot of wear and tear.

In 2023, the city announced that the catacombs would close for restoration. Now, after years of planning and hard work, Paris’s most gruesome attraction is once again open to visitors . . . if they’re brave enough to enter!

Paris, France, is a glittering city. But one of the spookiest sites on Earth lies beneath it. It’s a network of damp, narrow passageways. And they’re lined floor-to-ceiling with human bones! These are the Paris catacombs, a massive underground tomb. The catacombs hold the remains of more than 6 million people.

In the late 18th century, the graveyards of Paris were overflowing. Officials started putting old bones in tunnels under the city. That created the catacombs. The site was an instant hit with tourists. Today it draws more than 600,000 visitors a year. (See “Would You Rather . . . Spend the Night With Skeletons or Snakes?” in Science World, August 28, 2023.) But all those tourists have caused a lot of wear and tear. 

In 2023, the city made an announcement. The catacombs would close for restoration. The planning and hard work took years. Now, Paris’s most gruesome attraction is open again. Visitors can enter . . . if they’re brave enough!

Descending into the catacombs, tourists must pass under a sign that reads: “Arrête! C’est ici l’empire de la mort” (“Stop! This is the empire of death”). Though that may sound super-creepy, the Paris catacombs weren’t built to be a haunted attraction. “They were a solution to two crises afflicting Paris at the end of the 1700s,” says Erin-Marie Legacey, a historian at Trinity College Dublin in Ireland.

The first crisis was that the city’s streets were collapsing, says Legacey. For hundreds of years, builders in Paris had been mining limestone from beneath the city. They dug up this sedimentary rock and used it to construct most of Paris, including grand structures like the Notre-Dame cathedral and the Louvre museum (see “City of Limestone”).

After centuries of mining, the ground beneath Paris had become a maze of tunnels. Sometimes the tunnels collapsed, forming sinkholes. “Some people even fell into these holes!” says Legacey. In 1774, one sinkhole swallowed an entire street, including carriages, horses, and whole buildings.

As tourists descend into the catacombs, they pass under a sign. It reads: “Arrête! C’est ici l’empire de la mort” (“Stop! This is the empire of death”). That may sound super-creepy, but the Paris catacombs weren’t built as a haunted attraction. “They were a solution to two crises afflicting Paris at the end of the 1700s,” says Erin-Marie Legacey. She’s a historian at Trinity College Dublin in Ireland.

The city’s streets were collapsing. That was the first crisis, says Legacey. Builders in Paris mined limestone from beneath the city. For hundreds of years, they had dug up this sedimentary rock. They used it to construct most of Paris, including grand structures like the Notre-Dame cathedral and the Louvre museum (see “City of Limestone”).

After centuries of mining, the ground beneath Paris was a maze of tunnels. Sometimes the tunnels collapsed and formed sinkholes. “Some people even fell into these holes!” says Legacey. In 1774, one sinkhole swallowed an entire street. Carriages, horses, and whole buildings went down.

The second crisis affecting the city was that there wasn’t enough space in its cemeteries. At the time, most bodies were buried in large pits. Every few years, the bones were dug up and stacked in storage buildings to make room for new corpses.

In one cemetery at the center of Paris, the Cemetery of the Holy Innocents, this had been happening for more than 800 years. “People who lived near this cemetery kept complaining that it was too full, that it smelled, and even that it was making them sick,” says Legacey. Around 1780, the cellar wall of a neighboring building collapsed—and rotting remains burst through the hole! Something had to be done.

In 1786, Paris officials realized that they could solve both the sinkhole and cemetery problems at the same time. First, they cleaned up and reinforced the tunnels under Paris. Then they got to work emptying out the cemeteries. For months, they carted millions of bones to the tunnels under the cover of night and dumped them inside.

A second crisis affected the city. There wasn’t enough space in its cemeteries. Back then, most bodies were buried in large pits. Every few years, the bones were dug up and stacked in storage buildings. This made room for new bodies.

This had been happening for more than 800 years at the Cemetery of the Holy Innocents. It’s located at the center of Paris. “People who lived near this cemetery kept complaining that it was too full, that it smelled, and even that it was making them sick,” says Legacey. Around 1780, the cellar wall of a neighboring building collapsed. Rotting remains burst through the hole! Something had to be done.

In 1786, Paris officials had an idea. They could solve both the sinkhole and cemetery problems at the same time. First, they cleaned up and reinforced the tunnels under Paris. Then they emptied out the cemeteries. For months, workers moved millions of bones under the cover of night. They carted them to the tunnels and dumped them inside.

At first, the catacombs held disorganized piles of bones. But in 1809, Napoleon Bonaparte, the emperor of France, decreed that the underground burial chamber would be cleaned up and turned into a monument. Artisans worked for months, stacking larger bones—like leg bones and skulls—into intricate patterns. The catacombs quickly became a major tourist attraction. Unfortunately, living visitors created conditions that were damaging to the bones of the dead.

Paris’s underground tunnels are naturally chilly and damp from rainwater that seeps into the rock and drips from the limestone ceiling. Heat from visitors’ bodies and breath further increases humidity in the tunnels. Visitors also breathe out carbon dioxide gas, which collects in the enclosed space.

This combination of high humidity and excess carbon dioxide created the perfect conditions for mold and bacteria to grow. These organisms started eating away at the bone-covered walls, which began to crumble and crack. After two centuries of tourists trekking through the catacombs, they were ready for a major revamp.

At first, the catacombs held jumbled piles of bones. Then Napoleon Bonaparte, the emperor of France, ordered a change in 1809. The underground burial chamber would be cleaned up and turned into a monument. Artisans worked for months. They stacked larger bones, like leg bones and skulls, into intricate patterns. The catacombs quickly became a major tourist attraction. But living visitors created conditions that damaged the bones of the dead.

Paris’s underground tunnels are naturally chilly and damp. Rainwater seeps into the rock and drips from the limestone ceiling. Heat from visitors’ bodies and breath increases the humidity in the tunnels. Visitors also breathe out carbon dioxide gas. It collects in the enclosed space.

The result is a combination of high humidity and excess carbon dioxide. It created the perfect conditions for mold and bacteria to grow. These organisms started eating away at the bone-covered walls. The walls began to crumble and crack. For two centuries, tourists had hiked through the tunnels. The catacombs needed a major restoration.

In November 2025, the Paris Catacombs closed to the public. Over the next five months, architects, stonemasons, and electricians descended 18.3 meters (60 feet) underground to work around the clock renovating the cramped tomb.

Stonemasons carefully restacked sections of walls that had started to degrade. They couldn’t use cement to hold the bones in place—the wet paste would only increase humidity and weaken the remains. Instead, they wedged the bones together like building blocks.

To help protect and conserve the bones, workers replaced the ventilation system to improve air flow and control temperature, humidity, and carbon dioxide levels. Electricians also installed new lighting to better showcase the eerie structures.

Additionally, the catacombs received a major security upgrade. Paris’s sprawling tunnel network extends for hundreds of miles beyond the 1.5 kilometer (0.9 mile)-long stretch of bone-lined catacombs open to the public. Thrill seekers called “cataphiles” sometimes sneak underground to explore, make art, and have parties, says Legacey. The new security system will hopefully help prevent vandalism and other damage to the historical site.

The new and improved catacombs reopened on April 8, 2026. Renovators worked hard to preserve the site’s spooky and somber atmosphere. “The catacombs have basically looked the same since they were created more than 200 years ago, which is really fascinating,” says Legacey. Even with some modern upgrades, descending into the dark, cramped corridors is a “little bit like going back in time.”

In November 2025, the Paris Catacombs closed to the public. Architects, stonemasons, and electricians descended 18.3 meters (60 feet) underground. They worked around the clock. Over the next five months, they restored the cramped tomb.

Sections of walls had started to crumble. Stonemasons carefully restacked them. They couldn’t use cement to hold the bones in place. The wet paste would increase humidity and weaken the remains. Instead, they wedged the bones together like building blocks.

Workers replaced the ventilation system. The new system improves air flow and controls temperature, humidity, and carbon dioxide levels. This helps protect and conserve the bones. Electricians also installed new lighting. It showcases the eerie structures better.

The catacombs received a major security upgrade. A 1.5 kilometer (0.9 mile)-long stretch of bone-lined catacombs is open to the public. But Paris’s massive tunnel network extends for hundreds of miles beyond that. Thrill seekers called “cataphiles” sometimes sneak underground. They explore, make art, and have parties, says Legacey. The new security system aims to help prevent vandalism and other damage to the historical site.

The new and improved catacombs reopened on April 8, 2026. Restorers worked hard to preserve the site’s spooky and somber atmosphere. “The catacombs have basically looked the same since they were created more than 200 years ago, which is really fascinating,” says Legacey. The catacombs may have some modern upgrades. But descending into the dark, cramped tunnels is still a “little bit like going back in time.”