Sinkholes or dolines, form when an underlying cave passage collapses forming a depression on the surface above. The Didyma doline is about 80m in diameter and up to 30m deep. It lies in the slope of Mount Didimo, which comprises karstified limestone. At the foot of this mountain the rather flat valley ground is filled with limestone debris from Mount Didimo. Most likely a big cave system in the limestone caved-in twice, once below the flank of the hill and once below the valley ground. The image shows an olive grove in the foreground.