This lake is located at 540 m. above sea level. It has an area of 4,3 km². It is rather deep and has several coves. One of the main coves is Sesseliuvik, where the river Austura discharges the lake. The southeastern cove is Holmavik, where a short river Skamma enters the lake from Lake Rettarvatn. The northeastern cove is Atlavik. The lake abounds in lake char and brown trout but the catch can vary depending on the tackle, the weather and other circumstances. The permits are valid all around the lake and in the upper part of the East River. About 1/3 of the catch usually is brown trout.

There are several good and sheltered tent pitching spots around the lake. There is also 4 cottages for rent for anglers. The road from Laugarbakki (a hamlet in the north) usually is passable by 4wd vehicles during summer but the road from the farm Kalmanstunga in the west is rather difficult during the wet seasons.

It is not possible to drive around the lake. There is a short airstrip south of the cove Sesseliuvik. Lake Arnarvatn is mentioned in the Sagas (Grettis saga) and some of the topographical names are derived from them. On the small peninsula called Grettistangi is a ruin of a hut, which is well worth taking a look at.The distance via Laugarbakki from the capital is about 233 km by the Whale Bay tunnel and 55 km from the hamlet Laugarbakki. If you travel over the mountain pass Kaldidalur, past the farm Kalmanstunga, the distance from the capital is about 200 km.