Gullborgarhraun, a lava field in Hnappadalur from the Gullborg crater. There are some large and unusual caves in the lava field. One of these is Gullborgarhellir, considered one of the loveliest lava caves in Iceland, not least because of the unusual number of beautiful stalagmites and stalactites. The cave is a protected natural feature and can only be visited with a guide from the farm Heggstaðir. Some ruins nearby are believed to date from the Sturlunga age in the 13th century, when Aron Hjörleifsson had a hide–out in the lava field. It is said that his main hide–out was in a cave called Aronshellir. In 1979 one more cave was found in this lava field.