An Caisteal (Coll)

Dùn Foulag, located at grid reference NM17505908, was once thought to be a dun, though it is now considered to be only a naturally rocky knoll.

[1] It is located on the Inner Hebridean island of Coll, at grid reference NM17185815; situated about 300 metres (1,000 ft) west-northwest of Ballyhaugh farmhouse.

The early 20th century antiquary Erskine Beveridge considered Dùn Foulag to be a dun and thought he found evidence of a defensive wall.

This once supposed dun was visited in 1972 by the Ordnance Survey (OS) who could find no trace of antiquity on site; and currently the Royal Commission on the Ancient and Historical Monuments of Scotland (RCAHMS) classifies it a 'natural feature'.

[3] Traces of the fort are visible on a rocky boss, which reaches 12 metres (40 ft) above the surrounding ground.