It survives now only as a notation on a map, a shape recorded on the third edition of the Ordnance Survey six-inch series in 1930 and apparently gone from the ground before anyone thought to look more carefully.

Circular enclosures of this kind are among the most common archaeological features in the Irish landscape. They typically date from the early medieval period and served as enclosed farmsteads or ringforts, defined by an earthen bank and ditch that protected a household and its animals. The Ballynakill example, at around 43 metres in diameter, falls within the typical size range for such a structure. What makes its case quietly melancholy is what the 1930 map also records: the enclosure was already being cut by field boundaries running from the south-west to north-north-west and from the north-east to the south-east. Those boundaries did not merely cross the site; over time they apparently erased it. The progressive subdivision of land for agriculture, a process that accelerated dramatically in the post-Famine decades as holdings were reorganised and hedged off, is responsible for the disappearance of a great many earthworks across Ireland. At Ballynakill, the enclosure seems to have been one of them, its banks levelled and its ditch filled in as the field system expanded across it.