This natural fortress, somewhat fortified by the people in the area in the past, is situated on top of a 177 m high volcanic plug between Lake Vesturhop and the Vididalur Valley. No one knows for certain who added to the fortifications, when or why. It has been suggested that the people of the Huna District, who were under constant threat of attacks by the chieftains of Borgarfiord, used it for defence in the 13th century.