BERLIN — Be it ancient tombs, homes, abandoned mines, sanctuaries or shopping malls, humans have always been inventive when it comes to settling in underground spaces. But increasing rates of environmental disasters have raised fears of an impending climate cataclysm — and the prospect of humans forced to live below ground. Here are nine examples of our collective subterranean past that could inform our future:

GERMANY — Cave Hohler Fels in the Swabian Alps

When the first Homo sapiens took over Northern-Central Europe more than 40,000 years ago, they found shelter in caves. For the people of the Upper Paleolithic, these dwellings not only provided protection from the inhospitable climate of the later Ice Age, but also became important cultural hubs for the hunter-gatherers. In 2008, historians discovered one of the oldest representations of the human body ever discovered in a cave named Hohler Fels in the Swabian Alb: A goddess figurine carved out of mammoth ivory dubbed the "Venus of Hohle Fels". They also uncovered an almost entirely preserved flute made out of vulture bone, believed to be one of the first musical instruments ever found. To date, 80,000 stone tools and up to 300 pieces of jewelry have been recovered from the cave of Hohler Fels, which measures 500 square meters.

TURKEY — Cappadocia cities

According to the Greek historian Xenophon from the 4th century BC, in Cappadocia, the center of today's Anatolia, "the houses were under the earth," and to access them the "people descended on ladders." Even animals found a refuge here. When Christianity came to Asia Minor in the first century, believers in the remote region found these houses ideal as the rock was easy to work with, enabling whole cities to emerge underground. They were hidden and easy to defend thanks to their widely ramified labyrinths closed with stones. Numerous monasteries and about 3000 churches were carved here, and the caves remained sanctuaries until the Turkish invasion in the 11th century.

Cappadocia underground city (Turkey) — Photo: Pxhere

ITALY — Roman catacombs

The underworld was a fearful place for the ancient Greeks and Romans — it was darkness and death down there. For certain religious communities in the Empire, this made it an attractive place to bury their dead. Following the example of the Jews, Christians in the second century began digging tunnels, now reaching a total length of 170 kilometers, into the soft rock outside the gates of Rome. Archeologists count 60 catacombs in which about 850,000 parishioners were buried. Since the graves were regularly visited by relatives, these tunnels saw plenty of activity. There were even churches and meeting rooms for worship built down there, where mourning ceremonies following funerals took place.

Saint Sebastian Roman catacombs (Italy) — Photo: catacombe.org

ITALY — Rocks of Matera

Italy's Prime Minister Alcide De Gasperi once described it as a "national disgrace" and writer Carlo Levi even compared the "Sassi di Matera" with the "funeral hell of Dante". Over millions of years, the Gravina River had dug a deep gorge into the landscape of southern Italy's Basilicata. Over thousands of years, the caves of this gorge have been transformed into a unique urban landscape, with houses, apartments and churches. However, poverty and intolerable sanitary conditions prevailed, which is why De Gasperi resettled the residents in the 1950s. Since then, the caves have experienced an astonishing rise in tourism, making the UNESCO World Heritage Site list in 1993. Matera is this year's European Capital of Culture.

AUSTRALIA — Coober Pedy

The landscape in this part of South Australia looks like it has been ransacked by giant moles. You can see mounds everywhere. Coober Pedy is sometimes referred to as the opal capital of the world, as ninety-five percent of the world's opals come from Australia and a good deal are from Coober Pedy. Here, temperatures of over 40 degrees Celsius are not uncommon, so the small town has mainly expanded underground. First opal is mined, then the corridors and shafts dug into the stone are converted into houses and apartments. An underground house costs about as much as an above ground one. The advantage, however, is that the cave dwelling has natural air conditioning.

Coober Pedy underground church (Australia) — Photo: A. v. Z.

CHINA — Nuclear bunkers

The 60s were a time of nuclear war hysteria. The Chinese, for example, were particularly afraid of the Soviets, building a vast underground network of tunnels and open spaces between 1969 and 1979 to protect the inhabitants of Beijing. The network was meant to cover an area of ​​85 square kilometers, and the Chinese regime claimed that the facilities could hold all of the then six million residents, housing them for months in an emergency. The complex was equipped with restaurants, clinics, schools, theaters, factories and a roller-skating rink, as well as mushroom-growing areas. It has been closed down for renovation since 2008.

FINLAND — Safe swimming pool

In Helsinki you can swim many meters underground. The Itäkeskus swimming pool is one of at least 400 buildings carved into the granite stone below the Finnish capital, in addition to parking garages, metro tunnels, and kilometers of pathways connecting the subterranean buildings. And it doesn't stop there — an ice rink, a church, a bus station and an art museum were also built in the depths of the city. But no one is actually meant to live under the Earth here. The first underground buildings in Helsinki were constructed in the 1960s, and many more were built in the 1970s and 1980s, a time when inhabitants were seeking protection from any potential Soviet invasion.

The Itäkeskus swimming pool in Helsinki (Finland) — Photo: HKP Architects

CANADA — Montreal underground mall

It is called the "Ville intérieure" and is the largest underground city in the world with a tunnel system of 32 kilometers in length. When winter temperatures in Montreal, Canada, drop to minus 20 degrees Celsius, residents like to escape to this underground system of shops, hotels, cafes, theaters, cinemas and more. The original idea comes from urban planner Vincent Ponte, and was built between 1962 to 1992. So far, 80% of the city's office buildings and 40% of its shops are connected via this underground network. Universities, subway stations, an ice hockey stadium and more have also been integrated into the system. The nightlife in Montreal, ironically, is completely above ground.

MEXICO — Earthscraper

In 2009, the experimental architectural firm BNKR Arquitectura presented an "Earthscraper" to Mexico City. As the name implies, the building is the antagonist of the skyscraper. The building is supposed to reach 300 meters deep into the earth, and would be located in the Plaza de la Constitución, one of the largest squares in the world. This form of architecture avoids a serious problem: creating living spaces without affecting the surrounding historical buildings. The "Earthscraper" was planned as a reverse pyramid with a central cavity, so that even lower areas would be supplied with daylight. The base will be closed with a glass plate to guarantee that the above ground space is walkable.