The structure is modest in scale, a circular enclosure roughly 6.6 metres across, defined by the surviving base courses of a drystone wall built without mortar, the stones fitted together by careful selection and weight alone. The wall tapers slightly from its base, which measures about 0.6 metres thick, to its top, and where it still stands it reaches just over a metre in height. The collapsed upper courses have shed their rubble along the perimeter, most of it tumbled downslope to the north-east, leaving the arc of masonry looking more ruinous on that side than elsewhere.

The enclosure sits on a break in the steep hillside, the kind of shelf in the terrain that would have offered a degree of shelter and level footing in an otherwise demanding landscape. A narrow entrance, just 0.6 metres wide, opens to the north-east. Circular stone enclosures of this kind appear throughout the Irish uplands, and their uses were varied: some were animal pens, some served as small farmsteads, and some may have had functions that remain genuinely unclear. Without further excavation, this one at Glantrasna keeps its purpose to itself. What is certain is that someone chose this particular ledge on Droppa Mountain deliberately, shaped the slope's natural break to their own ends, and built something that has survived, at least partially, long enough for the bog to begin to reclaim it.