The area is also famous for its fairy chimneysrock formations, some of which reach 40 meters (130 feet) in height. Over thousands of years, wind and rain eroded layers of consolidated volcanic ash, or tuff, to form the sweeping landscape. From the 4th to 13th century CE, occupants of the area dug tunnels into the exposed rock face to build residences, stores, and churches which are home to irreplaceable Byzantine art.