Lake Anavatn has an area of 4,9 km² and is about 7 km long. Its greatest depth is 24 m and it is situated at 522 m above sea level. Its catchments area includes several brooks, but Thvera, its discharge, flows to the south to Lake Thverarvatn and then onwards to tribute to the glacial river Jokulsa a Fjollum by the farmstead Bru.
The lake is situated about 5 km from road no. 1 and is accessible by car from the north and the south. Just south of the lake are the ruins of the farmstead Heidarsel, which was the last to be abandoned in 1946. To the northeast of the lake are the ruins of the farmstead Veturhus on the lake Veturhusavatn. The catch consists of large lake char, 2-8 pounders. The distance from the capital is about 598 km by the Whale Bay tunnel and some 100 km from Egilsstadir.