The ancient Turkish city of Derinkuyu could house up to 50 thousand people, reached eleven stories below ground, and was built in the 7th or 8th century by Christians hiding from persecution. The story goes: In 1963, a man in the Nevşehir Province of Turkey knocked down a wall of his home. Behind it, he discovered a mysterious room. The man continued digging and soon discovered an intricate tunnel system with additional cave-like rooms. What he had discovered was the ancient Derinkuyu underground city, part of the Cappadocia region in central Anatolia, Turkey.

The elaborate subterranean network included discrete entrances, ventilation shafts, wells, and connecting passageways. It was one of dozens of underground cities carved from the rock in Cappadocia thousands of years ago. Hidden for centuries, Derinkuyu‘s underground city is the deepest.