Source: http://www.rdricketts.com/uncity.html

Underground cities are still being found in Cappadocia. The ancient Hittites, who came to area from east of the Black Sea around 2,000 B.C., are believed to have begun the excavation here. It is believed that these underground cities were enlarged during early Christians times to provide refuge from invaders and persecutors.

One of the largest of about forty such cities, called Derinkuyu, was found accidentally in 1963. Coincidentally, this is the same year that I left Turkey after my Air Force tour of duty there.

Derinkuyu is believed to have held up to twenty thousand people and could be as many as eighteen to twenty stories deep. Much of this underground city has not been explored due to cave-ins.

Large stones (similar to millstones) were rolled across the entrance from the inside to protect the inhabitants. A wooden shaft was inserted in the center hole of the stone to roll it into place.

Derinkuyu contains at least 15,000 ventilation ducts that provide fresh air deep within the underground city.

For over 4,000 years, outsiders have invaded the area of Cappadocia. During the last of the second millenium B.C., Assyrian trade colonies were in control. About 1,950 B.C., the Hittites came from the eastern Black Sea area to conquer Cappadocia. The Hittites were totally destroyed by the "Sea People."

The Assyrians again controlled the area about 680 B.C., the Medes (610 B.C.), and the Persians (550 B.C.). Cappadocian kings ruled from 332 B.C. to 17 A.D. The Romans and Byzantines ruled for about a thousand years.

After the Battle of Manzikert in 1071 A.D., the Seljukids captured Cappadocia. Although the area was under Muslim control, Christianity was allowed. In 1924, under a Greek-Turkish immigration exchange, all the Greek Christians left the area. The Christian presence here since about the first century A.D. came to an end. Only the fine works of Christian art were left.