Lake Langavatn has an area of 5,1 km². It is located 215 m above sea level with an area of 5,1 km² and its greatest depth is 36 m. It was created by the lava dam, which closed the valley during a prehistoric eruption. On its southeastern side is a refuge hut. River Langavatnsa enters the northern part of the lake and river Beila from the southeast. Its discharge is river Langa and at its exit a dam was built to regulate the flow to enable salmon rearing in the river.
The lake over abounds in lake char. It usually weighs no more than a pound, but there are occasional larger ones in-between. Brown trout is mostly caught near the mouths of the rivers entering the lake. Lake Langavatn is popular among families because of its richness in fish and natural beauty.