Biruaslum or Bioruaslam is a stack

Stack (geology)

A stack is a geological landform consisting of a steep and often vertical column or columns of rock in the sea near a coast, isolated by erosion. Stacks are formed through processes of coastal geomorphology, which are entirely natural. Time, wind and water are the only factors involved in the...

 in the Barra Isles

Barra Isles

The Barra Isles, also known as the Bishop's Isles as they were historically owned by the Bishop of the Isles, are a small archipelago of islands in the Outer Hebrides of Scotland. They lie south of the island of Barra, for which they are named. The group consists of nine islands, and numerous...

 of Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

, to the west of Vatersay

Vatersay

Vatersay is an inhabited island in the Outer Hebrides of Scotland. Vatersay is also the name of the only village on the island.-Location:The westernmost permanently inhabited place in Scotland, Vatersay is linked to Barra by a causeway completed in 1991...

. Approximately 2.5 kilometres (1.6 mi) from the nearest road, it reaches 72 metres (236.2 ft) 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

Fulmar

Fulmars are seabirds of the family Procellariidae. The family consists of two extant species and two that are extinct.-Taxonomy:As members of Procellaridae and then the order Procellariiformes, they share certain traits. First, they have nasal passages that attach to the upper bill called...

 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 2m wide and 3m high in places encloses a substantial semi-circular area. The wall is circa 50m long and best preserved at the south east end. Attached to the uphill side of the wall are the remains of a small oval structure about 19m2 in area. The style of the fort is similar to Iron Age

Iron Age

The Iron Age is the archaeological period generally occurring after the Bronze Age, marked by the prevalent use of iron. The early period of the age is characterized by the widespread use of iron or steel. The adoption of such material coincided with other changes in society, including differing...

 structures known from Ireland but the only datable finds so far discovered are of Neolithic

Neolithic

The Neolithic Age, Era, or Period, or New Stone Age, was a period in the development of human technology, beginning about 9500 BC in some parts of the Middle East, and later in other parts of the world. It is traditionally considered as the last part of the Stone Age...

pottery.