In 1963, an inhabitant of Derinkuyu (in the region of Cappadocia, central Anatolia, Turkey), knocking down a wall of his house cave, discovered amazed that behind it was a mysterious room that he had never seen, and this led him room to another and another and another to it … By chance he had discovered the underground city of Derinkuyu, whose first level could be excavated by the Hittites around 1400 BC
Only eight can be visited at the highest levels; others are partially blocked or restricted to archaeologists and anthropologists who study Derinkuyu.
Cool. This would make a great start to an aventure movie. I’d love to find something like this in my basement!