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.
It was opened to visitors in 1969 and to date, about half of the underground city is accessible to tourists.