Borgarvirki is a prominent landmark on the way through the Huna District. This natural fortress, somewhat fortified by the people in the area in the past, is situated on top of a 177 m high hill between Lake Vesturhop and the Vididalur Valley. The fortress has 10-15 m high natural ramparts with a 5-6 m deep depression in the middle. The man made part with the main entrance was reconstructed in 1949-1950.
Two ruins of human habitation and a fresh water well are inside the fortress. 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. Twiceit is supposed to have been under siege and both times the armies from Borgarfiord had to leave without results.