Derinkuyu Underground City, Turkey

Derinkuyu Underground City is an ancient multi-level underground city of the Median Empire in the Derinkuyu district in Nevşehir Province, Turkey. Extending to a depth of approximately 60 m, it was large enough to shelter approximately 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.