In the land of Efra-Hvol you can find three man-made caves collectively called Efra-Hvolshellar, which translates as Upper-Hvol Caves. They are dug into a rather coarse breccia that most likely originated from tillite deposits. The lower part is more fine grained showing a combination of horizontal, cross-bedded and prograding strata. There are three Upper Hvol Caves, two of which are joined together where the third considered to be the 2nd longest man-made cave in Iceland, measuring some 45 metres in length. However, because a section of the roof collapsed about 100 years ago, one can only go a third of the way into the cave. The Upper-Hvol Caves are a protected natural site
As a section of the roof of Stóri hellir (Big cave) collapsed partly about 100 years ago and the cave got filled with soil and dirt. In consultation with The Cultural Heritage Agency of Iceland, the cave has been partly dug out and one can only go a third of the way into the cave today. The Upper Hvol Caves are a protected natural site.
The caves in Upper-Hvol have historically been referred to as ‘the Irish Caves’ which are set into the so-called “Irish Heath”. It was originally thought that many of these man- made or artificial caves were made in the 19th century, but in fact, their historical names appear to confirm that they originated even before the settlement period.