Lake Réttarvatn in Arnarvatnsheiði is on the border of V.-Húnavatnssýsla and Mýrarsýsla, although mostly in the former. Its size is 2.1 km², maximum depth is 2 meter and it is at about 550 m above sea level. From it, river Skammá falls in a waterfall to Arnarvatn stóra. There are a lot of good fish in Réttarvatn, mostly Arctic char but some brown trout. Unlike the reputation of Arnarvatn stóra, the road to Réttarvatn is bad. The reason for this is the lack of roads from Arnarvatni stóra, as well as from Borgarfjörður and Stórasand. Anglers should not embark on this trip except in well-equipped 4-wheel drive vehicles with tires no smaller than 38” in size. From Arnarvatn stóra it is no than 10 km to Réttarvatn, but it takes about an hour to drive this way from the huts.