The older of the two is an enclosure of the kind found widely across Ireland, a roughly circular area defined by a low earthen bank, almost certainly prehistoric or early medieval in origin. The newer one, probably a sheepfold from within the last few centuries, was built directly over it, its builders either unaware of or indifferent to what lay beneath.

The older enclosure measures about ten metres across internally, its surrounding bank averaging 1.7 metres wide and standing to around 0.7 metres in height. An entrance gap, 1.4 metres wide, faces east. Circular enclosures of this type served a variety of functions in early Irish society, from settlement boundaries to livestock management to ritual use, and without excavation it is rarely possible to say which applied in any particular case. What makes Macha Ghrianáin notable is the layering itself: a ruined sheepfold collapsing back into a much older earthwork, the two structures slowly merging into a single grassy ring on the Iveragh landscape. The site was documented by A. O'Sullivan and J. Sheehan in their 1996 archaeological survey of the Iveragh peninsula, published by Cork University Press, which remains the principal reference for the prehistoric and early historic monuments of south Kerry.