Knútsstaðaborg hollow is an open cave, or lava chamber, about 10 square metres (107 square ft.) in size.
Explore this area on a self drive tour in Iceland.
It is a site surrounded by beauty; birch trees and heather grow all around, and the 2000-year-old lava fields, from the largest eruption in the area since the Ice Age, form fascinating and dramatic shapes across the landscape.
Many have compared the lava to the famous Dimmuborgir in the Mývatn area, which is nicknamed ‘the Dark Fortress’ due to the scale of its unusual formations. The Knútsstaðaborg hollow is a lovely location for photos or to stop and picnic, and, unlike many lava caves in Iceland, is safe to enter. Be prepared, however, for the strong smell of wool inside. During inclement weather or intense sunshine, the free-roaming sheep of the area tend to flock inside for shelter.