The enclosure measures roughly 87 metres east to west and 79 metres north to south, making it a substantial feature, yet it has been levelled to the point where its presence is felt rather than seen. What remains is a low, wide, grass-covered earthen bank encircling a gently saucer-shaped interior, with a gap 28 metres wide opening to the east. Attached to that eastern side, just outside the break in the bank, is a D-shaped annexe, a secondary enclosure roughly 36 metres by 35 metres, surviving as a raised platform about 45 centimetres high with a barely perceptible external fosse, the shallow ditch that would once have marked its outer boundary.

The site appears on Ordnance Survey six-inch maps from 1842, 1905, and 1937, each time rendered with hachures indicating an earthen enclosure of roughly 80 metres in diameter. On the earliest of those maps, the 1842 edition, trees are shown planted around the interior perimeter, suggesting the feature was still recognised and perhaps deliberately framed as a landscape element at that point. Enclosures of this general type are commonly associated with early medieval settlement in Ireland, where a roughly circular raised bank, sometimes with an annexed area for livestock or other activity, defined both a domestic space and a boundary between the inhabited and the open. No internal features have been recorded at Kilmacoom, which limits what can be said about its original function, but the morphology, a primary enclosure with a secondary D-shaped annexe, fits that broader tradition reasonably well. The enclosure and its annexe are also visible as a cropmark in aerial photography, the buried remains creating differential growth in the vegetation above them, which is often how levelled earthworks like this are first properly mapped.