Near Cappadocia in Turkey, under the town of Nevsehir, lies an amazing end extraordinary underground complex known as the Derinkuyu underground city. So far, there are more than forty underground cities discovered in that region of Turkey, of which Derinkuyu is the biggest spanning more than 8 levels and going as deep as 80 meters, and able to accommodate thousands of people at a time. The underground complex is complete with ventilation shafts, wells, water tanks, apartments, stables, communal rooms, and tombs, and is secured by 1000-pound stone doors that can only be opened from the inside. Each level could be isolated from the other levels, even though all levels access one another. More than 600 entrances to the city exist, and most are hidden.

Until recently the origin and purpose of the city were unknown when the Turkish Department of Culture dated the city built in the 8th century BCE by the Phrygians. The town was later enlarged during the Byzantine era, probably by the Christians whom historians believe used it as a hiding place during the first years of their persecution. The church that exists on the lowest floor may verify this theory.

Other theories related to the creation and purpose of these underground cities look to extra-terrestrial origins. One such theory is that the city was built by extra-terrestrial beings who later abandoned the city. Another theory speculates that the city was created by humans to protect themselves from air invasions or attacks by extra-terrestrial beings.

Derinkuyu is very well preserved and visitors can explore the first eight levels of the complex. It is an impressive site to visit and creates many questions regarding the massive efforts required to build such an underground city. What is its purpose? That question is yet to be answered.