Hæðargarðsvatn is a small and friendly lake right next to Kirkjubæjarklaustur and the road that goes down to Meðalland or Landbrot lies past it. The lake is about 0.16 km² and is 22 m above sea level. There is no visible flow from it, nor into it, but the water is renewed by underground streams that are in the lava all around the lake. There is a lot of fish and a lot of good brown trout, often 4 pounds in weight. It is believed that sea trout juveniles enter the lake through an underground stream and therefore part of the fish there is in fact sea trout. The best fishing is in early spring and until June, and it is not uncommon for anglers to fish at night. There, it’s possible to have wonderful moments in the twilight.