Derinkuyu underground city is an ancient multi-level underground city located in the Derinkuyu district in Nevşehir Province, Turkey. The city is considered to be the largest excavated underground city in Turkey. It could accommodate as many as 20,000 people together with their livestock and food stores. Caves may have been built initially in the soft volcanic rock of the Cappadocia region by the Phrygians in the 8th–7th centuries BC. However, the city at Derinkuyu was fully formed in the Byzantine era in the 8th century AD.