The monument consists of a natural island, fortified by an enclosure wall, forming an approximate rhomboid on plan, which lies about 150m from the S shore of Loch Maree.
The natural bedrock, visible around the shores of the island, supports a stone wall enclosing an area measuring approximately 36m E-W by 44m N-S along the diagonal axes of the quadrangle. The wall revets and runs along a natural rocky bank around the island. The enclosure wall is of rubble construction, well-coursed from roughly- squared stones apparently set in a clay mortar.
It is approximately 1m thick and, including the external revetment, stands to a height of over 1.5m in places. The area enclosed forms a level plateau at a higher level than the outer side of the enclosure wall, and acted as a courtyard. Towards the S corner of the courtyard lies a roughly-square, sunken, stone-walled pit approximately 5.5m square and over 1m deep. The stone lining remains to a height of 4 or 5 courses for most of the wall circuit.
The fortification, called a castle, is considered to have been a stronghold of the MacBeaths, who are presumed to have come here from Assynt during the 13th century, and after their ousting from the area by the MacLeods around 1430 it may have passed to the latter family. The MacLeods themselves had lost control of the area by about 1513. The site may well have earlier origins and have acted as the natural equivalent of a crannog.
It is similar to sites elsewhere called duns, and is similar to several such sites in the Uists. The area to be scheduled includes the whole island to the water's edge, as defined in red on the accompanying map. It is irregular on plan and measures a maximum of 75m N-S by 60m.