The underground cave site of Derinkuyu, Turkey, commonly referred to as “Cappadocia”, is an underground network of caves and tunnels which date back to the prehistoric era, as evidence of stone tools have been uncovered at the site. Experts believe that 20,000 – 60,000 people inhabited the Cappadocian caves with indication of air vents and water wells making it theoretically possible to live underground for extended periods of time, spanning years even. Stone wheels made of volcanic basalt were fashioned to create what’s referred to as “self sealing doors”. The rocks would be rolled in front of a pathway making entry impossible for invaders due to the inability to gain leverage. The only possibility of entry would be to cut through this wheel, often up to 1’ thick in width, which would waste valuable time giving those upon the other side time to prepare a counter attack