The bank that originally defined its circular boundary has been levelled, most likely through centuries of agricultural use, but the shape of the place persists. The Ordnance Survey map of 1838 recorded it clearly: a circular enclosure roughly 32 metres in diameter, still coherent enough at that point to be plotted with confidence.

What makes this particular site quietly notable is the souterrain attached to it. A souterrain is an underground stone-lined passage or chamber, typically associated with early medieval settlement in Ireland, and thought to have served as a place of refuge, storage, or concealment. They are fairly common features within ringforts, the enclosed farmsteads that were the dominant settlement type in Ireland from roughly the fifth to the twelfth centuries, but their presence always implies a degree of deliberate construction and social organisation that goes well beyond simple pastoral life. The ringfort at Hundred Acres, with its associated souterrain, suggests a settlement of some standing in the early medieval landscape around Lough Mask and Lough Carra, an area whose archaeology was documented in a local survey compiled by D. Lavelle in 1994.

Today, the earthwork survives only as a faint rise in the grass, its bank gone and its underground passage unexcavated. The site sits in working pasture, which explains both its gradual erosion and the fact that it has not been disturbed more thoroughly. What remains is less a monument than a trace, the kind of place that rewards a careful eye rather than a casual glance.