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.
Between the third and fourth levels is a vertical staircase. This passage way leads to a cruciform church on the lowest (fifth) level.
The large 55 m ventilation shaft appears to have been used as a well. The shaft also provided water to both the villagers above and, if the outside world was not accessible, to those in hiding.
Nevşehir Province has several other historical underground cities and Derinkuyu itself connects to Kaymakli via an 8 km tunnel.
The underground cities and structures are carved out of unique geological formations. They may have been used as hiding places during times of raids. The locations are now archaeological tourist attractions. They remain generally unoccupied. In excess of 200 underground cities containing a minimum of two levels have been discovered in the area between Kayseri and Nevsehir. Some 40 of those contain a minimum of three levels or more. The cities at Kaymaklı and Derinkuyu are two of the best examples of habitable underground structures.