It is a rath, the Irish term for a ringfort, one of the most common archaeological features in the Irish countryside. Ringforts were typically circular enclosures defined by one or more earthen banks and ditches, used as enclosed farmsteads during the early medieval period. Thousands once existed across Ireland, but centuries of agricultural pressure have reduced a great many to traces this subtle or less.

The enclosure at Garranereagh measured approximately twenty metres in diameter, a modest size even by the standards of single-bank raths. It was still legible enough in 1842 to be mapped by the Ordnance Survey, rendered on their six-inch sheet as a hachured circle, the conventional notation surveyors used to indicate a raised or banked earthwork. At some point after that survey was made, the site was levelled, most likely as farmland was improved and field boundaries reorganised. A low bank persists to the north, but the broader circuit has been all but effaced. To compound matters, field clearance stones, the cobbles and boulders grubbed out of nearby ground during agricultural work, have been tipped onto what remains of the bank and across the interior, further obscuring whatever profile once existed.