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, 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.
Caves may have first been built in the soft volcanic rock of the Cappadocia region by the Phrygians, an Indo-European people, in the 7th–8th centuries B.C., according to the Turkish Department of Culture. When the Phrygian language died out in Roman times, replaced with Greek, to which it was closely related, the inhabitants, now Christian, expanded their underground caverns adding the chapels and Greek inscriptions.
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). The city was connected with other underground cities through miles of tunnels. Some artifacts discovered in these underground settlements belong to the Middle Byzantine Period, between the 5th and the 10th centuries A.D.
These cities continued to be used by the Christian natives as protection from the Mongolian incursions of Timur in the 14th century. After the region fell to the Ottomans the cities were used as refuges (Cappadocian Greek: καταφύγια) from the Turkish muslim rulers.
As late as the 20th century the locals, called Cappadocian Greeks, were still using the underground cities to escape periodic waves of Ottoman persecution. Dawkins, a Cambridge linguist who conducted research on the Cappodocian Greek natives in the area from 1909-1911, recorded that in 1909,
When the Christian inhabitants of the region were expelled in 1923 in the Population exchange between Greece and Turkey the tunnels were abandoned.
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.