Derinkuyu underground city

The Derinkuyu underground city (Cappadocian Greek: Μαλακοπή) is an ancient multi-level underground city in the Derinkuyu district in Nevşehir Province, Turkey. Extending to a depth of approximately 60 m (200 feet), it is large enough to have sheltered as many as 20,000 people together with their livestock and food stores. It is the largest excavated underground city in Turkey and is one of several underground complexes found across Cappadocia.

• http://en.wikipedia.org/wiki/Derinkuyu underground city