The Derinkuyu underground city was built by the Phrygians in the period between 8th and 7th centuries BC. The city has been built built in the soft volcanic rock of the Cappadocia region. This underground city has been used as a refugee settlement , during the Persian Achaemenid empire. The Derinkuyu underground city was connected through tunnels with other underground cities, such as the underground city of Kaymaklli. Some of these underground tunnels are up to 50 miles long.
The Derinkuyu underground city could accommodate around 20,000 people. Had it’s own cellars, refectories, storage rooms, chapels, oil and wine presses etc. On the second floor there is a room with a barrel vaulted ceiling. It is thought that this room served as a religious school.
The Dereinkuyu underground city was opened in 1969 and only the half of the city is available for tourists.
Source
Source
Derinkuyu underground city stone doors
The stone doors have the height of 1-1.5 meters , they are wide 30-50 centimeters and they weight around 200 to 500 kilograms. The hole in the middle has been used to open and close the doors or just to see who is outside.
Source
