What is recorded here

Cairston belonged to a family of Gordons from at least the 1620s, but the castle may be older. The Orkneyinga Saga places Earl Harald inside a fortress off Cairston on Michaelmas Day, and the Bu is the only nearby candidate large enough to match that story. Whether Harald fought inside these walls or the broch behind them cannot be known, but the tale gives the ruin a shape: a place important enough to be seen from the sea and strong enough to hold a man against a fleet for a whole day.

Scotland's National Record of the Historic Environment records Bu of Cairston as Castle (medieval). The official map says its point is accurate as follows: NGR given to the nearest 10m. The record does not by itself mean that the public may enter the place.

The historic-place record does not grant public access. Check current conditions and ownership before entering land or a building.