Hnausapollur is a stunning blue lake nestled in a crater that formed about 1100 years ago in a short explosive eruption. It is about 30 hectares in area and is one of those lakes in Iceland that are known by two names: Hnausapollur and Bláhylur. It lies in a crater near Mt. Tjörvafell, just north of Lake Frostastada, at an altitude of 570 metres. It looks a lot like its neighbor, Ljótapollur, but the access and drop from the edge of the crater down to the lake is considerably easier. There are special brown trout in the lake, but they are small and few feel it worth clambering down to fish for them. A ring road skirts the crater edge and from there it is a quick walk to go up to the highest point for a still better view.