3D laser scan of the Iron Age souterrain at Cracknie, northern Scotland. Souterrains were common on Iron Age settlements in Scotland, and many have been recorded on the northern mainland. Those in this area are usually stone-lined, built with drystone walls and heavy stone lintels capping an underground passage. Like most souterrains, the Cracknie example curves, meaning the end of the passage is not visible from the entrance. The precise purpose of souterrains is not certain: most were probably used for food storage but, like many Iron Age structures, it may be difficult to disassociate symbolic, ceremonial or ritual concerns.