The Derinkuyu underground city (Cappadocian Greek: Ανακού) 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 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 about half of the underground city is currently accessible to tourists.
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The tunnels were rediscovered in 1963, after a resident of the area found a mysterious room behind a wall in his home. Further digging revealed access to the tunnel network.[13]

In the Cappadocia region of Turkey there is a town called Derinkuyu; and beneath Derinkuyu there is a city, vast and deep, of ancient design, preserved to this day. The mystery of who built it and why remains, although scholars have their theories.

The city at Derinkuyu was fully formed in the Byzantine era, when it was heavily used as protection from Muslim Arabs during the Arab–Byzantine wars (780-1180).