Mousa Broch is the finest example of a 2000 year old Iron Age tower or broch anywhere. It stands 13.3 metres high. The island of Mousa can be reached by boat from Sandwick. Most Brochs have been dismantled throughout time by succeeding dwellers who found other uses for the stone. Also, living habits changed and so such structures were no longer considered practicable or desirable. However, the Mousa example has remained more or less unchanged over the last 2000 years due, largely, to its remote location.
Storm petrels (alamooties) nest within its stone chambers. Feeding far out to sea, these tiny swallow like birds return to their nests under the cover of darkness to avoid other larger predatory seabirds.