As the overpopulation of megacities grows, architects are increasingly beginning to develop underground space under cities. BBC Future's correspondent talks about several unusual structures hidden under the earth's surface - from houses hewn in rock in Australia to bomb shelters and basements in Beijing, where up to a million people live.
Underground running track in Helsinki
In many ways, Bernadette Roberts' three-bedroom home is unremarkable. “Living room, dining room, kitchen - we have all the amenities, just like in a regular home,” she says.
But this is not an ordinary house: it is located underground. Roberts lives in Coober Pedy, 846 km north of the Australian capital Adelaide. The town is known as the world capital of opals, which are mined here by the mine method. Another attraction of Coober Pedy is underground houses carved into the rock, in which 80% of the local population live.
Coober Pedy is an inhospitable place. The air temperature here can reach 50 ° С. A hundred years ago, miners came to the conclusion that it is much cooler underground. This is how the underground city appeared.
According to Roberts, "on cool days," when the surface temperature is around 40 ° C, her underground house is cool - about 25 ° C: "The impression is that you are in a room equipped with air conditioning."
Coober Pedy is not the only place on Earth where local authorities have decided to build inland. But the reasons for this decision are different everywhere.
Promotional video:
Bedroom of an underground house in Coober Pedy
According to forecasts, by 2050, two-thirds of the world's population will live in cities. Accordingly, urban land will become a very limited resource. Due to a lack of space, the presence of state-protected areas and other factors, many megacities can no longer grow up and in breadth. Isn't it time to dig?
Singapore is one of the most densely populated metropolitan areas on the planet. A population of almost 5.5 million people huddle in an area of only 710 square meters. km. “In the case of Singapore, the main reason for underground development is lack of land,” says Zhou Yingxin of the Metropolitan Underground Research Center, a nongovernmental organization of urban underground planners and analysts.
Zhou continues: “Until now, Singapore has been expanding its territory with sand from the deepening of the seabed, but this technology has exhausted itself. The sea is getting deeper, the territory of the city-state is approaching the state borders, the sand is getting more expensive, neighbors are complaining, and so on."
Underground Church at Coober Pedy
The Singapore government is considering plans to build the Underground Science City, a 300,000 square meter research center. km, which would lie at a depth of 30 to 80 m underground. It is expected to house research facilities, including biomedical and biochemical laboratories, which will employ 4,200 people.
Sometimes the lack of land is explained by bans on the development of historical territories. In Mexico City, for example, there are strict restrictions on building in the historic center. For this reason, architecture firm BNKR Arquitectura has designed a giant underground residential complex in the form of an inverted pyramid 300 meters deep, known as the Earthscraper.
According to the project, 5000 people will live in the building. The terraced floors will be illuminated by natural light streaming through the huge glass ceiling. However, the lower floors will require additional fiber optic lighting.
Esteban Suarez, co-founder and head of BNKR, expects Zemleskreb to inspire architects to design other new buildings.
Underground Science City Project in Singapore
Meanwhile, in Beijing, the growing demand for affordable housing is forcing people to go underground and live in much more modest conditions.
Annette Kim, director of the Spatial Analysis Lab at the University of Southern California, recently spent a year in Beijing studying the city's underground dwellings - mostly former bomb shelters and conventional basements converted into small dormitories.
She says: “Living conditions near Beijing are very different. I saw terrible poverty, but to my surprise, some of the dwellings were quite good by Beijing standards."
Millions of underground inhabitants
How many people live on the "underground floor" of Beijing? According to Kim, official estimates range from 150,000 to 2 million: “I'm used to rounding up to one million. This is an incredibly large number."
Project "Zemleskreba" in Mexico City
Kim says the situation is due to two factors - the construction boom in China, which has led to an increase in the supply of underground space, and the lack of affordable housing. In recent years, a large number of rural residents have moved to Beijing in search of a better life, but many of them do not have a residence permit in the capital, without which they cannot expect to receive housing on the surface. All these people can afford is underground life.
A completely different type of underground structure is being built about 1000 km south of Beijing. The 300-room Shimao Wonderland Intercontinental Hotel is cut into the rock of an abandoned quarry with a depth of 90 m, located 35 km south-west of Shanghai.
Although the quarry provides a convenient site for in-depth construction, initially many believed that nothing would come of it, according to Martin Jochmann, project director for design in charge of the concept.
Shimao Wonderland Intercontinental Hotel in Suburbs of Shanghai
“Building a hotel is incredibly difficult because it's kind of turned upside down,” says Jochman. "For example, unlike conventional buildings, the contents of the water and sewer pipes will have to be pumped upward with pumps."
But this design also has its advantages. The topography of the quarry creates its own microclimate - in summer the rock accumulates heat, and in winter it slowly releases it like a heating radiator. The temperature factor drives people into the ground and in the capital of Finland - Helsinki. The city has already created 9 million cubic meters. m of underground facilities, including shops, a jogging track, a hockey arena and a swimming pool.
Eija Kivilaakso, lead masterplanner for Helsinki's underground development, explains that conditions underground are sometimes much more favorable than on the surface - especially in winter, when outside temperatures can drop below -20 ° C: “In our climate, you start to appreciate the opportunity to work or sit with a cup of coffee underground without having to go outside in the rain or cold."
Fear of the Dungeons
Thus, the construction of underground living spaces is technically possible. But would people want to spend long periods of time underground? The success of projects like the Mexican "Zemleskreb" largely depends on whether its potential residents will be able to overcome the fears associated with being under the earth's surface.
"Zemleskreb" is designed in such a way that its residents do not feel claustrophobic
“The human mind is prone to fear underground spaces, which it associates with dark, cramped caves and the danger of being buried alive,” notes Suarez.
However, he hopes that people's perceptions of underground life can be changed by combining all sections of the Zemleskreb with a spacious central open space illuminated from above by natural sunlight - like a natural deep canyon.
For some people, the very thought of being underground in a confined space can be terrifying. Gunnar Jenssen, researching the design of underground spaces and the psychological aspects of their use for the benefit of the Scandinavian organization SINTEF, says that about 3% of the world's population suffers from pronounced claustrophobia, and they have no obvious exit from the premises, fear of flooding or fire can cause very severe stress. However, these fears can be dealt with.
“If you give these people the illusion of being in control, they feel calmer,” Jenssen says. "This is exactly what we are doing - we are introducing such illusions into architecture and design."
He continues: “The bare essentials are fresh air as well as adequate (or at least subjectively sufficient) space. To visually expand the room, you can use optical illusions, but it is better if it is really spacious and well lit."
Lowline Underground Park Project in New York
Jenssen has worked on four of the longest road tunnels in the world. For the illusion of space, he creates in the tunnels well-lit oases with palm trees and imitation of the sky above them: “You are driving through a dark tunnel and suddenly you drive into a brightly lit place with trees and plants. You have a feeling of free space, as if you are breaking free into an open area - despite the fact that you are still following a tunnel cut through the mountain at a depth of 1000 meters."
Illusions and other design tricks to create a more comfortable underground environment may help, but would underground dwellers suffer the negative effects of lack of sunlight?
According to Lawrence Palinkas of the University of Southern California, lack of sunlight can lead to sleep disturbances, poor mood and hormonal dysfunctions, which in turn can cause various chronic diseases. However, according to him, "a well-established regime and regular exposure to bright lighting, similar in characteristics to sunlight, will allow people to live underground for a long time."
Under the ground for a while
So, theoretically, people can live underground. But will this happen in reality? Annette Kim, who has personally researched Beijing's underground dwellings, believes what will happen: "We will have to go underground if urbanization continues at its current pace."
According to her, it all depends on how the underground space is used: “Many of those living in Beijing's undergrounds go underground only for the night. During the day, they enjoy the sunshine and fresh air on the surface."
Li Huangqing, a postdoctoral fellow at Nanyang Technological University who is writing her doctoral dissertation on underground urbanization, says most cities are not planning underground dwellings, but multi-purpose spaces that will be occupied by malls and highways. This will free up space on the surface for the construction of new housing, the creation of green areas and entertainment centers.
According to Zhou, it makes sense: "There is no reason people cannot live underground, but there are so many things that need to be put underground before that."
Kieran Nash, BBC Future