Biruaslum
Biruaslum or Bioruaslam is a stack in the Barra Isles of Scotland, to the west of Vatersay. Approximately  from the nearest road, it reaches  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  wide and  high in places encloses a substantial semi-circular area. The wall is  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  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. See also
 Funzie Girt

Notes

References
Keith Branigan (2007) Ancient Barra: exploring the Archaeology of the Outer Hebrides. Comhairle nan Eilean Siar. Francis G. Thompson (1974) The Uists and Barra. David and Charles. James Fisher Rockall: The Islet of Birds. Barra Isles
Stacks of Scotland