Kalmanshellir is in Hallmundarhraun and was protected in 2011. The cave system is approx. 4 km long and is protected as a natural monument. Kalmanshellir is the longest known lava cave. The cave structure is very diverse, with wide spaces interlaced with narrow channels and numerous openings on the surface. The aim of the protection is to preserve the unique geological formations in the cave, and the cave system as a whole, and to prevent damage to the geological formations.


Traffic through the cave is subject to special permission from the Environment Agency. Part of the cave is closed for access and all traffic is prohibited, unless in the vital interest of the public as estimated by the Environment Agency and managing parties.