In 1963, a man living in Turkey decided to do a little home renovation. He knocked down a wall and found a strange room on the other side. A little terrified, he kept digging and discovered an intricate tunnel system winding through an underground city that went 85 meters (280 ft) underground.
It was Derinkuyu, an ancient underground city built between the 12th and 15th centuries BC. The underground complex was used by the Hittites to hide as many as 20,000 people from enemy raids. Today, tourists can explore the caves and see a whole city that was hiding on the other side of a man’s wall.