In 1963, a man broke down a wall in his home and discovered a mysterious underground city.

In the depths of the Turkish city of Derinkuyu, there is an entire world that reaches 85 meters (279 feet) into the earth. Covering an eastern area and with a network of laryngeal tunnels, Derinkuyu was lost to history until 1963 when a man accidentally discovered a tunnel behind one of the walls of his house. The underground city is actually 18 stories deep, with wells, chapels, stables, schools, and more, and is said to hold up to 20,000 people.

Going deeper into the earth: the “forgotten” city of Derinkuyu

Carved out of the region’s soft volcanic rock, known as tuff, within the Cappadocia region of Turkey, the creation of the underground city was an incredible feat. The complex is an impressive example of ancient engineering, complete with ventilation shafts, shafts, water tanks, and an extensive network of passages and tunnels.

It is believed that there are more than 600 entrances to the city, most of them hidden, to the last underground city that covered 445 km2 (172 mi2). There are stables, apartments, common rooms, chapels, tomes, and even wine and oil presses. The hallways are “secured” with 1,000-pound (454 kg) stone doors that can only be opened from the inside.

For the sake of greater security, each level could be isolated from the others, even though all levels could access each other. “Those lying on the lower levels…were able to cut off the water supply to the upper and lower levels, preventing enemies from poisoning the supply,” explained a report in IFLS. “The tunnels could be locked from the inside with round rolling stone doors, and the corridors themselves were narrow to force visitors to line up one at a time.”

What is more surprising is that this network of tunnels and living spaces was abandoned and forgotten. IFLS reported that Derinkuyu was only rediscovered in 1963, when a local man used a sledgehammer on its wall and came face to face with an entire underground world carved out of the soft rock. It was added to the UNESCO World Heritage List as a site titled Göreмe National Park and the Rock Sites of Cappadocia.

The underground cities of Cappadocia

Derinkuyu is not the only underground city in Cappadocia. In fact, it is said to be just one of 200 safe underground shelters that have been discovered carved into the rock of volcanic ash, including Kayákli near Neʋsehir and Mazi near Urgup. Some claim that Derinkuyu residents could ʋvisit other underground cities ʋthrough an extensive network of tunnels.

As recently as 2015, National Geographic reported the discovery of another underground city beneath a hilltop castle in Neʋşehir during the construction of a local housing project. Riʋalling Derinkuyu in size, “the site appears to have been a large self-contained complex with air shafts and water channels”. Initial studies by Neʋşehir University seemed to conclude that the site was 113 meters (371 ft) deep and covered five million square feet (460,000 square metres), making it larger than Derinkuyu.

Who built the Derinkuyu underground city?

Until recently the origin and purpose of the city was unknown. According to the Turkish Department of Culture, the city was built 2,800 years ago, in the 8th century BC, by the Indo-European Phrygians. It was later enlarged during the Byzantine era, proƄaƄally for Christians, who were used by Ƅelieʋe historians as a hideout to avoid persecution.

The church that exists on the lowest floor can verify this theory. As recently as the 20th century, it was also used as a place to escape persecution during the Ottoman Empire. <eм>Culture Trip </eм>explains that the underground city was abandoned after 1923 with the expulsion of Christians from the Turkish government and was only rediscovered in the 1960s.

But, there are alternative theories. Some claim that the underground city was built by the Anatolian Hittites in the 15th century BC to flee from enemies. Others have hypothesized that the underground cities were created during the Younger Dryas event around 14,500 years ago, when a comet broke up and segments exploded within Earth’s atmosphere, spewing dust and soot into the atmosphere and leaving out the sun for months, causing temperatures to drop and plunging the world into an Ice Age. This theory posits that these underground cities would have been created at the same time as GöƄekli Tepe, just 600 kilometers (370 mi) east of Derinkuyu.

As usual, there are also those who associate the creation and purpose of these underground cities with aliens. One such theory is that the city was built by aliens who later left the city. Another speculates that the city was created by humans to protect themselves from aerial and alien invasions.

As Jim Willis said in an Ancient Origins article, “Only one thing is known for sure. They are there. Someone built them a long time ago, perhaps further back than modern archaeologists are willing to admit. The original builders must have had a compelling reason to pull off such an audacious feat, but then they were lost to history, their presence completely forgotten. And nobody knows why.