Biruaslum

Biruaslum or Bioruaslam is a stack in the Barra Isles of Scotland, to the west of Vatersay. Approximately 2.5 km from the nearest road, it reaches 72 m in height and there is a ruined prehistoric fort on the southern side. Francis G. Thompson characterizes it as "high and virtually inaccessible"; James Fisher mentions a "fulmar flying up and down its tiny cliff."

Cliff-fort
The vertical cliffs on the east side of the islet that separate it from Vatersay protect the site from the sea and a well-constructed wall that is 2 m wide and 3 m high in places encloses a substantial semi-circular area. The wall is 50 m long and best preserved at the southeastern end. Attached to the uphill side of the wall are the remains of a small oval structure about 19 m2 in area. The style of the fort is similar to Iron Age structures known from Ireland but the only datable finds so far discovered are of Neolithic pottery.