While redoing his house in 1963, a man in the Nevsehir Province of Turkey, in an area known as Cappadocia, knocked down a wall. He was probably not thinking that much of it. However, instead of seeing something expected, he found himself looking into a tunnel.
What he had found, unbeknownst to him at the time, was the ancient underground city of Derinkuyu. Derinkuyu was an entire city carved into the stone below Cappadocia, reaching some 60 meters down. It had 18 levels, and included residences, churches, food storage, wineries, and even a school. It was designed to house some 20,000 people as well as a number of livestock. It features vents to the surface and several discreet entrances like the tunnel found behind the wall. These hidden entrances suggest that the city was built as a precaution in order to shelter the population in times of war or natural disaster.
This large room with its vaulted ceiling was used as a religious school. The city of Derinkuyu was used by Christian populations from the early Middle Ages up until the early 20th century.
One of the massive stone doors that would block off entrances. The hole in the center would be fit with a beam so the door could roll open and shut.
The city was built to shelter people in times of strife. During peacetime, it was mainly used for storage.
An illustration of an underground city like Derinkuyu. Note the church on the bottom level. Cities like this were used during times of Christian persecution, so religious items would be placed on the lowest levels for protection