The remains of the Broch of Clickimin, Shetland.
Brochs are iron age dwellings unique to certain areas of Scotland.
Typically they are a tower with an inner and outer wall of a drystone construction. A spiral staircase runs between the walls allowing access to the upper levels.
It is thought that they were probably a status symbol - possibly belonging to the chief, but also defensive, and when under threat other families could take shelter within, even bringing the livestock into the central areas.
The best remaining example of a broch is the Broch of Mousa in The Shetlands, which stands over 13 m high.
Visitors there can still climb the staircase between the walls.