Lake Gunnarssonavatn lies on the border of the district Myrarsysla. It has an area of 2,38 km² and located at 541 m above sea level. A brook meanders from its northern side through many lakes and changes names quite a few times on its way. It abounds in lake char and brown trout.
The fishes have one defect, they are infested with worms, which, however, do not seem to limit their growth.
According to the legend, two brothers, the sons of Gunnar, went up to the lake one hard winter to fetch food for the starving people at home. They caught many fishes, among them a few with reversed fins, which they consumed and died from the poisonous flesh. The distance from the capital over the mountain pass Kaldidalur is about 200 km.