This is a promontory fort, a type of enclosure in which a headland does most of the defensive work, with the sea guarding three sides and human effort applied only where the land connects. Here, that effort took the form of a low earthen bank, roughly a metre high, thrown across the narrow neck of the promontory, with a shallow fosse, or ditch, cut on both sides of it. It is modest by the standards of the form, but the logic is the same as at the great cliff-edge forts found elsewhere along the Irish Atlantic coast.

The sub-rectangular area it encloses is substantial, and the interior has its own quiet complexity. A natural geological fault divides the space along its axis, effectively splitting the enclosure into two levels without anyone having to lift a stone. On the lower, eastern side, a rectangular hut site measuring approximately six metres by three metres survives, along with several groupings of stones whose arrangement does not fit neatly into obvious categories. Such promontory forts are generally associated with the Iron Age in Ireland, though many remained in use or were reoccupied across later periods, and the presence of a hut foundation here suggests the site was more than a temporary refuge or a purely symbolic boundary. Bear Island itself sits at the mouth of Bantry Bay, and any settlement commanding this particular spur of land would have had a clear view of one of the most strategically significant stretches of water on the south-west coast.