The underground city can hold 20,000 people

TURKEY Located more than 85 m below ground and consisting of 18 floors, Derinkuyu is the largest underground city in the world ever discovered.

The tunnel leading to the underground city of Derinkuyu. Photo: Travel Turkey

Beneath the cobblestone streets of Derinkuyu city lies an ancient network of tunnels and rooms that could have sheltered 20,000 people, according to IFL Science . The labyrinthine complex beneath Derinkuyu is one of a series of underground cities around Nevşehir province in central Turkey, listed as a UNESCO World Heritage Site. A similar population was found near Cappadocia, 30 km to the north.

The underground city of Derinkuyu was rediscovered in 1963 when a local man repeatedly lost his chickens. After noticing the chickens had fallen into a crevice during home repairs, the owner found a dark passage leading to the colony. There are hundreds of houses in the area that also have hidden entrances to such an underground urban area.

Interspersed between the nooks and crannies of the complex are rooms that were once used as meeting places, cattle sheds, kitchens, warehouses, and small prisons. The building even has an efficient ventilation system that allows fresh air to circulate deep within the maze structure.

Throughout its long history, the underground city of Derinkuyu has primarily served as a refuge during war or difficult times. The age of the city remains controversial among scholars, but some estimates put the building to 2,800 years ago. Most likely the underground tunnel was used by people in the Achaemenid Empire founded by Cyrus the Great in 550 BC. After that, the underground city continued to be used as a hiding place by the Arabs during the Arab - Byzantine war between 780 - 1180.