The circular earthwork, once roughly twenty metres across, was recorded on the Ordnance Survey's six-inch map of 1842 as a hachured enclosure, the cartographers' conventional shorthand for a raised or embanked feature visible from the ground. At some point after that survey, it was levelled entirely, leaving no surface trace whatsoever.

Ringforts, known in Irish as raths, were the most common form of enclosed settlement in early medieval Ireland, typically consisting of a circular bank and ditch enclosing a domestic area used by a farming family. Thousands survive across the country in varying states of preservation, but many have been lost to agriculture over the centuries, particularly during periods of intensive land improvement and field reorganisation. The Grenagh example fits this pattern. The notes also record extensive field fence clearance in the surrounding area, suggesting the landscape around it has been substantially reshaped. What the 1842 map caught was, in all likelihood, already one of the last reliable impressions of the monument before the ground was worked flat.