Derinkuyu Underground City

Derinkuyu (Turkish pronunciation: [derˈinkuju]) also known as Elengubu, is an ancient multi-level underground city near the modern town of Derinkuyu in Nevşehir Province, Turkey, extending to a depth of approximately 85 metres (280 ft). 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 throughout Cappadocia.

Source: wikipedia