This enormous underground city that once housed around 20,000 people was accidentally discovered by a man after knocking down a wall in his basement. Archaeologists revealed that the city was 18 stories deep and had everything needed for underground life, including schools, chapels, and even stables
The underground city at Derinkuyu could be closed from the inside with large rolling stone doors. Each floor could be closed off separately.
The city could accommodate up to 20,000 people and had amenities found in other underground complexes across Cappadocia, such as wine and oil presses, stables, cellars, storage rooms, refectories, and chapels. Unique to the Derinkuyu complex and located on the second floor is a spacious room with a barrel-vaulted ceiling. It has been reported that this room was used as a religious school and the rooms to the left were studies.
Starting between the third and fourth levels are a series of vertical staircases, which lead to a cruciform church on the lowest (fifth) level.
The large 55-metre (180 ft) ventilation shaft appears to have been used as a well. The shaft provided water to both the villagers above and, if the outside world was not accessible, to those in hiding.
Caves might have been built initially in the soft volcanic rock of the Cappadocia region by the Phrygians in the 8th–7th centuries BC, according to the Turkish Department of Culture. When the Phrygian language died out in Roman times, replaced with the Greek language, the inhabitants, now Christian, expanded their caverns to deep multiple-level structures adding the chapels and Greek inscriptions.
In 1963, the tunnels were rediscovered after a resident of the area found a mysterious room behind a wall in his home while renovating. Further digging revealed access to the tunnel network