Underground city of Derinkuyu

In 1963, an inhabitant of Derinkuyu (in the region of Capadocia, central Anatolia, Turkey), was demolishing a wall of his house-cave, and discovered astonished that behind the wall was a mysterious room that never had been seen; this room took to another one, and this one to another one and another one...By chance the underground city of Derinkuyu was discovered, whose first level could be