Lake Thernuvatn is the largest of the three with an area of 1,6 km². It is shallow and situated 122 m above sea level. It has an island in its centre and several brooks feed it. Its discharge, Thernulaekur, tributes to river Kollavikura. Lake Hvilftarvatn has an area of 0,2 km².
It is shallow and at 120 m above sea level. A brook connects it with lake Deildarvatn (0,4 km² and shallow). Road no. 85 passes between the lakes. The catch consists of lake char and brown trout and lake Hvilftarvatn is favoured.
The distance from the capital is about 648 km by the Whale Bay tunnel.