“Halt! You are here in the Kingdom of Death,” warns the macabre inscription at the entrance to Les Catacombes de Paris – the underground boneyard filled with the remains of 6 million Parisians, which attracts half a million living and breathing visitors each year.



This 1.5km-long ossuary (still one of the French capital’s most profitable tourist attractions) is dwarfed by the city’s 300km of underground tunnels that are closed to the public. New discoveries occur regularly, such as the recent gallery found beneath the Bois de Vincennes, one of Paris’s largest parks.

Next to the catacombs, a former toll house known as the Barrière d’Enfer (“Gate of Hell”) hosts the Inspection Générale des Carrières (IGC), an office created in 1777 by King Louis XVI to oversee the mapping and maintenance of the 32 sq km of abandoned quarries below the surface of the French capital – an underground space 10 times the size of New York’s Central Park.



Dramatic sinkholes, such as the recent one in Japan, are not always caused by underground mining – but Paris’s subterranean history certainly makes it more vulnerable to such events. While the last cataclysm dates back to 1961, when 22 people died in the collapse of a whole neighbourhood on Paris’s outskirts, the IGC still makes more than 70 interventions each year on incidents such as collapsing houses, or roads disappearing into sinkholes.

The abandoned quarries beneath Paris may be its most misunderstood and underrated piece of architecture

The exploitation of chalk, gypsum and especially limestone endowed Paris with the cream-coloured stones used for the Louvre and in buildings of the Haussmann era. Indeed, a city’s aesthetic is traditionally determined by the material available for its construction. Quarrying took place outside the city proper, in what were then semi-rural areas such as Montmartre and Montparnasse.

In the early stages of modern urbanisation, however, these villages were soon absorbed by the expanding Paris – making those quarries that were not already exhausted no longer accessible or too expensive to mine.

The names of the last two managers of the quarry remain on the wall at the entrance. Photograph: Justinien Tribillon

Left abandoned and with no record of their locations, this myriad of underground quarries became a hidden peril for a city in full expansion. In 1774, in the first major event of its kind, 300 metres of a street in Paris collapsed into a 20 metre-deep hole. No one was killed, but this dramatic incident triggered the creation of the quarry inspectorate.

More than two centuries later, the IGC’s knowledge of the underground is incredibly detailed – yet they still regularly stumble across unchartered spaces. I have an early morning meeting with Julien Alaterre, the 27-year-old head of the IGC, to inspect the newly discovered gallery under the Bois de Vincennes.

As we begin our 19-metre descent down a steep flight of stairs, Paris’s underbelly soon reveals three striking features: high humidity, absolute silence, and an unexpectedly warm temperature. The underground spaces remain at a constant temperature of 14C – a stark contrast to the freezing January weather above ground.

The newly discovered gallery is only a fraction of the well-known, four-hectare Brewery Quarry that has been left unexploited since the 1860s. Alaterre explains it is Paris’s best-preserved quarry, with large spaces up to six metres high.

Opening it to the public has been in the pipeline for 20 years, and the quarry is set to be one of the sites suggested for redevelopment as part of an upcoming design competition launched by the city’s mayor, Anne Hidalgo (the second edition of Reinventing Paris will this time focus on Paris’s underground spaces).

Paris’s Underground Atlas produced by the IGC: underneath the city lies 300km of tunnels. Photograph: Courtesy of IGC and Mairie de Paris, 2017

The quarry still bears the marks of its industrious past: on the walls, the writing of the last quarrymen to exploit its limestone (mining in Paris was eventually banned in the 1860s); on the floor, a rusted plaque with the name of a local beer (Brewery Quarry was subsequently used for the production and storage of beer). There are also worn-out furrows on the ground – throughout the 20th century, empty quarries were used to produce quantities of button mushrooms known as “Champignon de Paris”; today they are mainly imported from China.



Access to the newly discovered gallery has been sealed off, however. Heavily damaged and a threat to the park’s administration buildings overhead, the condemned gallery will receive an injection of several thousand cubic metres of concrete to fill and stabilise it.

While the IGC is often criticised for neglecting to preserve the city’s underground heritage, Alaterre contends that injections of concrete are often the most affordable and efficient technique to avoid further damage both below and at the surface.

Beyond emergency action, the IGC’s role is to prevent risk, and to inform and advise Parisians on what lies beneath their feet. French law is clear: a landlord owns their house, the ground and underground of their property. If a house starts to sink in the ground, it is up to the property owner to foot the bill, not City Hall. Considering that 20% of Paris’s surface area is faced by such a threat, you might want to check with the IGC before signing off the purchase of your new pied-à-terre.



IGC engineers visit the Carrière de la Brasserie (Quarry of the Brewery) in Paris. Photograph: Justinien Tribillon

Any large real estate or public infrastructure project faces the same risk: according to Alaterre, consolidating Paris’s underground represents 25% of any new metro line’s budget. This was the case in 1900 when the first lines opened, and still is today with the Grand Paris Express.

Living above a former quarry is not always regarded as a burden. Xavier Niel, one of France’s wealthiest people and a known “cataphile” (those who illegally explore Paris’s catacombs and underground quarries), is said to have built a flight of steps that goes directly from his house down to Paris’s undergrounds.

Access to the quarries is, however, strictly forbidden. “The first reason,” Alaterre says, “is that it’s not a public space; by definition, you go under people’s houses and therefore on to their properties. And then it’s also very dangerous.” He explains this as we navigate our way through a claustrophobic tunnel right beneath the Place Denfert-Rocherau in central Paris.

The IGC headquarters possesses a buried bunker built during the second world war, with an armoured door that leads directly to the quarries. The space here is very narrow and you often have to bend, almost crawl, to progress. The humidity is very high – the walls and ceilings ooze with water, and in places you walk through ankle-deep puddles of mud.

Paris’s guts don’t smell, however, beyond the scent of a very old cave. This network of quarries lies much deeper than the city’s sewers, and there is no light other than the one you bring. The effort required to crawl through this subterranean maze, coupled with the heat, means you soon get dehydrated.

Graffiti left on the wall of the underground galleries. Photograph: Justinien Tribillon

Yet it is also easy to understand the fascination cataphiles have for this space – walking down the galleries, accompanied by a deafening silence and utmost darkness is like navigating through the guts of the city. Everywhere graffiti, empty cans of beers and burnt candles offer evidence that, while visiting the quarries might be illegal, it remains a hobby for many.

“It gets quite crowded on weekends,” Alaterre admits.

There is an ambiguous relationship between Paris’s authorities and its cataphiles. The IGC is not in charge of policing the quarries; that is up to a team of trained police officers nicknamed the “catacops”, who declined to be interviewed for this article.

While circulating the quarries is illegal – you risk a fine of up to €60 – neither the IGC nor the police seem to mind the veteran cataphiles who possess a good knowledge of the underground space, and who respect their heritage. Yet the police are much stricter towards “tourists” who visit the underground for the first time, and those organising underground raves and concerts here.

Back at the surface, Paris’s familiar hustle and bustle suddenly feels like an aggression. Beyond its quirkiness and fascinating character, the 300km network of abandoned quarries that lies beneath may be the most misunderstood and underrated piece of architecture in the French capital.

Paris’s underground space could certainly play a role in addressing some of the challenges faced by cities: the need for low-carbon solutions, spaces for urban farming and small-scale industry, telecommunication infrastructure and data centres, even nightlife venues in dense residential areas.

Redeveloping the abandoned quarries would require significant financial investment from both public and private investors. Yet while quarrying stopped for security concerns in the 19th century, the use of the underground space for the culture of mushrooms or the production and storage of beers only stopped for economic reasons.

The challenges of urbanism in one the world’s densest cities are fast changing, and the quarries could yet play a renewed role in Paris’s development – in addition, of course, to visitors’ never-ending fascination with the Kingdom of Death.

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