Just a few kilometers south of the Geothermal area Seltún at Krísuvík is a small lake, Grænavatn (Greenlake). The lake is a volcanic crater that got its name from its unusual green color. The color is due to a high level of sulphur in the water and its depth. The lake is only about few hundred meters in diameter and offers a perfect trail for a refreshing walk, as it only takes about 20 minutes to walk around the lake. For a small lake it is quite deep, though, or 45 meters. This is visible as you stand by the brim, and you can see how the color changes by the shoreline where the lake gets deeper. Grænavatn is considered by geologists to be one of the most noteworthy geological phenomena of its kind in Iceland.
A failed venture that almost destroyed the lake
Many visitors wonder what the deal is with the two silage towers and the decaying cowhouse right by the lake. This is one of those unfortunate projects initiated at a time when understanding of nature was limited, and respect for natural wonders easily gave way for economic ventures. Although this was not such a long time ago, in the fifties, the whole project almost ruined the lake as some of its surroundings were altered in the process. Needless to say, the whole venture failed, and the people and the Hafnarfjörður municipality behind it have not yet had the decency to remove this horrible building and heal the area around the lake.
Grænavatn and folklore
Due to its unusual nature and color, the lake has been a source of folklore stories throughout the centuries. Only as recently as the middle of the 16th century an odd creature was spotted coming from the lake. The lake is almost on the main road Krísuvíkurvegur (42) and can be seen as you pass by it only a few hundred meters from Seltún the geothermal area.
Below is the location of Grænavatn lake on the map of Iceland