Catacombs of Paris

The first thing you notice is the air. It is cool and damp, and it carries a faint mineral smell, like wet chalk after rain. Your footsteps change too. The bright noise of Place Denfert-Rochereau disappears above you, and each step on the spiral staircase sounds closer and softer. You are going down roughly twenty metres, below the metro, the sewers and the roots of the trees. Down here the temperature stays cool all year, whatever the season is doing on the street above.

Before we meet the dead, let us talk about the stone. Paris was built from what lies beneath it. For centuries, workers cut pale limestone out of the ground here to build the city's churches, bridges and grand apartment houses. Geologists call it Lutetian limestone, after Lutetia, the Roman name for Paris. So when you look at a cream-coloured facade on a Paris boulevard, you may be looking at stone that once filled these very tunnels. The city above is, in a real sense, the hollow you are walking through.

That hollow became a danger. By the eighteenth century, much of southern Paris sat on top of old, forgotten quarries. Streets cracked. Houses sank. In 1774, a section of road near here collapsed into the ground, and the shock pushed the royal government to act. In 1777, King Louis the Sixteenth created a special service to inspect and reinforce the quarries. Its first head was an architect named Charles-Axel Guillaumot. That service still exists today, and you will see its work all around you.

Look at the walls as you walk through the first long galleries. You will notice carved inscriptions with letters and numbers. These are the marks of the quarry inspectors. Many of them name the street directly above your head, so the tunnels mirror the map of the city. Some carry dates from the late eighteenth century. The thick stone pillars and walls around you were built to hold up the ground. Without them, the neighbourhood above could have slipped into darkness.

Now, a surprise most visitors walk past too quickly. Along this route there are small sculptures carved directly into the rock. They show a fortress with towers and walls. They are usually credited to a quarryman called Décure, an old soldier who, according to the story, carved from memory the port of Mahón, on the Spanish island of Minorca, where he had once served. Legend adds that he died in a cave-in while building a staircase nearby. That last part is a tale, not a record. But the carvings are real, and they are delicate.

So how did the bones arrive? In the heart of old Paris, near today's Les Halles district, stood the Cemetery of the Holy Innocents. For centuries, the city had buried people there layer upon layer. By the 1780s, it was overflowing, and neighbours complained of the smell and of illness. The authorities closed it. The underground quarries offered a solution. In 1786, this place was blessed as an ossuary, which means a place where bones are kept, and the transfers began.

The moving was done mostly at night. Carts covered with black cloth rolled through the dark streets, with priests walking alongside and singing prayers for the dead. The bones were tipped down shafts into the quarries below. Over the following decades, other cemeteries across Paris were emptied in the same way. In the end, the remains of around six million people came to rest down here. That is more than twice the population of Paris today.

And now you reach the doorway. Above it, carved in French, are the words, Arrête, c'est ici l'empire de la Mort. In English, Stop, this is the empire of Death. It is a theatrical welcome, and it is meant to be. Beyond it, the walls change. They are no longer stone. They are made of human bones, stacked with care, sometimes higher than your head. Take a moment here. Let your eyes adjust before you move on.

The neat arrangement you see is not from the first years. At first, the bones were simply piled in heaps. In the early nineteenth century, a new inspector, Louis-Étienne Héricart de Thury, turned the ossuary into something closer to a monument. Workers stacked the long leg bones into solid walls. They set skulls into lines, crosses and even heart shapes. Behind this decorative front, the smaller bones lie loose and unsorted. What you see is a careful facade, built for the living.

Notice the stone plaques set into the bone walls. They name the cemetery the remains came from, and the year they were moved. You will also find poems and quotations about death, chosen by Héricart de Thury, some from the Bible and some from French and Latin writers. Here and there stand small structures with their own purpose. One stone basin collected water from a spring. A stone lamp once held a fire, which helped move the air through these still galleries.

The ossuary soon drew curious visitors, and it opened to the public in the early nineteenth century. Over the years, it attracted writers, nobles and later the photographer Nadar. In the 1860s, he brought electric lights underground and made some of the earliest photographs taken with artificial light. Because his exposures were long, he sometimes used mannequins in place of workers. It is a strange thought. Some of the first pictures made in darkness show the dead and some dressed dummies.

The route you are walking is only a small part of a much larger network. Hundreds of kilometres of old quarries run beneath the city, and almost all of them are closed to the public. Entering them is forbidden. Still, a community of underground explorers, known as cataphiles, has long roamed them. During the Second World War, the French Resistance used a shelter beneath this square during the liberation of Paris in 1944. Paris has always had a second life underground.

As you walk on, pay attention to the silence. Water drips somewhere ahead. Voices from other visitors drop to a murmur without anyone asking. The floor can be wet and uneven, so move slowly, and keep a hand free. The bones themselves are fragile, and many show the marks of countless passing fingers. Please look but do not touch. The people resting here once walked the same streets you walked this morning, bought bread, crossed the same river.

Soon you will climb a long staircase and step out onto a quiet street, some distance from where you entered. The light will feel very bright. The traffic will sound very loud. Before you hurry off, look at the pale stone of the buildings around you. Think of the tunnels beneath your feet, and the millions who rest there. Paris is a city built on its own foundations, and, quite literally, on its own past.