6. Derinkuyu Underground City (Turkey)
Derinkuyu, located in the Cappadocia region of Turkey, is an ancient multi-level underground city extending to a depth of approximately 85 meters. It is large enough to have sheltered as many as 20,000 people together with their livestock and food stores. The city features a complex network of tunnels, rooms, and ventilation shafts, including a large 55-meter ventilation shaft that appears to have been used as a well. Each floor could be closed off separately with large rolling stone doors, providing defense against invaders. The city also includes amenities such as wine and oil presses, stables, cellars, storage rooms, refectories, and chapels. Derinkuyu is the largest excavated underground city in Turkey and is one of several underground complexes found throughout Cappadocia. (en.wikipedia.org).
