Lake Hafravatn is just outside the capital limits, 76 m above sea level. It has an area of 1,02 kmē. Its greatest depth is 28 m. The river Seljadalsa enters it from the east and its discharge is Ulfarsfellsa. It abounds in small lake char and the occasional much larger brown trout.

Salmon also enters the lake, but is very rarely caught. On the lake are quite a few holiday houses and the ruins of a sheep pen, which was used to sort out the sheep up to the seventies.

The distance from the capital is about 14 km.