In the morning, even as the square of La Défense fills with people, it’s in the depths of the city, at –65 underground, that the anthill really moves. In 2038, the city of Paris is now underground, sprawling like tentacles under the surface. A dystopia, or an inevitable reality? Most cities today have already maxed out their potential for surface growth while the urban population continues to grow. Will the cities of the future be built dug out beneath the reach of the sun’s rays?

A necessity by 2030

Under the city, the city! Always more vulnerable to hostile climates, and especially dense, cities are increasingly seeing themselves grow in three dimensions. Urbanization is growing so rapidly that the United Nations estimate that by 2050, two in three people will be city dwellers – which means 2.5 billion more people to house. The basements of Paris, Tokyo, and even New Delhi are attracting more and more architects, urbanologists and city planners because, often devoid of life, the subterranean domain seems ripe for investment.

From a few meters deep to hundreds of floors below, the underground could someday welcome more than fiber optics, sewers, and metro lines. As forecasts increasingly affirm the possibility of underground construction of housing, parks, and other living spaces, the subterrain could initially become a cellar for fuels and electrical systems, freeing up space on the surface.

Investing in city undergrounds is necessary to make the cities of tomorrow more sustainable. They are temperate spaces, with less variability in temperature than the surface, as well as conserving heat for future energy savings. Furthermore, potable water would be more easily preserved, thanks to fewer contaminants from surface wastewater. Lastly, geothermal energy already allows us to produce heat and cold by using resources underground. Goodbye to saturated and polluted surfaces, hello to new, responsible, ecological possibilities!

A profound idea

The idea of cities sunk six feet under might sound straight out of a dystopia. But it really comes from the past. Still today, archaeologists are discovering traces of civilizations built underneath their feet. Ahead of its time in this respect, Turkey can claim several subterranean cities, particularly in Cappadocia, where Derinkuyu was discovered in 1963. The name of the city, which was built in the 8th century BCE, literally translates to “deep well.” It was dug 13 stories underground.

Places of worship, of storage, stables, kitchens and workshops: everything was taken care of for its inhabitants to live (almost) as they would on the surface. At the time, these kinds of cities dug into tufa were mainly places of refuge where thousands of people could hide out in case of an enemy invasion or a meteorological disaster.

Multiplying the underground

More recently – and therefore closer to what an “underground city of the future” might look like – Montreal has often been cited as an example of underground urban growth. Since 1962, its inhabitants can practically live their lives by taking underground tunnels leading to RESO, its underground pedestrian network. Along 32 km of tunnels, one can find all the commodities of modern life, from a restaurant to a hotel and passing by several boutiques. Even if the challenges of its construction aren’t exact perfect models of modern subterranean urbanism, other cities seem ready to take up new challenges.

Helsinki is still creating its own master plan, but the city of Singapore is already underway with a project underneath its island. The city-state has invested more than $188 million in engineering and research to develop this form of urbanism. The government also modified its property rights laws; all basements now belong automatically to the state. In 2019, Singapore should be set to unveil its master plan concerning the future of subterranean spaces and the exact manner in which they’ll be developed.

Although some cities are already partially underground, others are undertaking more modest projects, or they’re concentrating first on revaluing existing spaces. In Seoul, a university was dug into the bowels of the earth by the French architect Dominique Perrault, as was Paris’ Bibliothèque François-Mitterrand and Berlin’s velodrome, of which passers-by can only see the roof. In London, urban farms known as Growing Underground are located 30 meters down and grow salad greens, thanks to a clever LED lighting system.

In Paris, calls for projects were launched through the program Réinventer Paris 2. The goal? Breathe new life into tunnels, parking lots, cellars, and defunct metro stations by turning them into living spaces. The city is interring itself more and more, growing where the sun don’t shine. The Louvre is investing in more and more basements to preserve its oeuvres, the Halles are renovating themselves under concrete slabs, and the 45,000 square meters of unoccupied space in La Défense have been revalued through the culinary project Table Square.

In two years, from 2015 to 2017, the Lowline Lab in New York welcomed curious visitors to view plants growing underground thanks to an innovative solar technology. Built in an abandoned Lower East Side market, this futuristic laboratory was situated two blocks from the actual Lowline, the former underground tramway terminal that James Ramsey and Dan Barasch now hope to turn into a park. The first underground green space should see the light of day (metaphorically) in 2021 and could change the dark image some underground cities have. It includes a device that brings natural light underground, which would considerably improve the quality of life of people living there and would constitute a strong argument for subterranean living.

A reachable goal

The development of a modern underground city is on a different scale than Montreal’s RESO and more complex to build than Derinkuyu. There’s electricity, water storage, transport, connectivity, budget, and even property to think of… and all of that extending into the long term. There are so many technological challenges that French participants are “doubtless ready to rise to the challenge,” according to Bruno Barroca, an urban engineering interviewed by France Culture. It’s a reachable goal only if planners, architects, engineers and geologists work together and share data to create a viable project to exploit the riches of the underground. Only with this kind of synergy of skills will these cities get built.

The American researcher Michael Doyle firmly believes this. He was present at the conference titled “Building the City Under the City” in Lyon in July 2017, part of the think tank La Fabrique de la Cité. “We need to share available data on the ground and underground about subterranean constructions, water, energy, so we can create relevant mapping tools,” he explains. The goal is to optimize connectivity with the surface, but also to allow for good horizontal and vertical circulation underground. In this manner, “basement cities” will be sustainable and able to serve future generations, which will be able to transform and reinvent them at will.

The fear of the underground

For years, Elon Musk has been working on connecting spaces between. The billionaire has developed a new generation of tunnel boring machines to unite underground networks in record time. With his business The Boring Company, the American is counting on revolutionizing transport by 2021 with high-speed electric shuttles built underneath Los Angeles.

His is a futurist project that divides the field. For many, it’s the antithesis to the image of a vibrant underground. “It’s clear to see from the illustrations of The Boring Company that the underground is a sort of black hole, completely empty. That plays right to people’s fears of the underground environment, of claustrophobia,” Australian city planner Elizabeth Reynolds said at La Fabrique de la Cité’s conference.

The price of life in the shadows

Another big question is one of property. Futurist thinkers are well aware of it. Public powers will need to address it so that “we don’t end up with a patchwork of private tunnels without any link between them,” Guillaume Lavoie, Montreal’s municipal councilor, said at the same conference.

Last, building in the depths of cities costs money, about 1.5 times more than surface construction. But even if this cost is inevitable, it’s important to keep one’s eye on the long term, Bruno Barroca says. Cities built underground carry promises of considerable energy savings and a priceless quality of life.

For revitalizing abandoned areas and building autonomous subterranean cities, underground construction is one of the major problems facing the future of urbanization. From the vertigo of the 52nd floor of the Tour FIrst of La Défense to the claustrophobia of an apartment at the –12th floor, it’s only one step away!