Underground City, Derinkuyu, Nevşehir Province, Turkey

Features
One of the heavy stone doors. They have a height of 1–1,5 m, 30–50 cm in width and weigh 200–500 kg. The hole in the centre can be used to open or close the millstone, or to see who is outside.
The underground city at Derinkuyu could be closed from the inside with large stone doors. Each floor could be closed off separately.
The city could accommodate up to 20,000 people and had all the usual amenities found in other underground complexes across Cappadocia, such as wine and oil presses, stables, cellars, storage rooms, refectories, and chapels. Unique to the Derinkuyu complex and located on the second floor is a spacious room with a barrel vaulted ceiling. It has been reported that this room was used as a religious school and the rooms to the left were studies.