Arnarsetur is a short monogenetic volcanic fissure with scoria and spatter craters, formed in an eruption that was an integral part of the Reykjanes Fires, a volcano-tectonic episode from 1210 to 1240. The fissure is two kilometers in length and the lava formations that originate from it cover 20 square kilometers. They are rugged and contain lava tubes and remains of human activity. The name Arnarsetur means Eagle’s nest and derives from a pair of eagles that lived in the area before.
Arnarsetur is located east of the road to town Grindavík (43). The exit is about half way from Reykjanesbraut (41) to Grindavík.