Oia is located on top of a hill at the edge of the caldera, at about 150 m (500 ft) elevation. The strong, dry north wind that blows every summer (the famous meltemi) provided the residents with a cheap, renewable, and dependable power source. The windmills at the highest point of Oia were probably built in the 18th century to ground flour and serve as bakeries. They were focal meeting points and an indispensable source of prosperity and sustenance.