What makes it immediately interesting is not just its age but its geometry: a roughly subcircular central area about 5.2 metres across, ringed by a fosse, which is the term for a deliberately cut ditch, measuring 1.2 metres wide and up to 0.7 metres deep, and then beyond that an external bank. The whole monument averages around 12.25 metres in overall diameter, making it a compact but coherent piece of prehistoric engineering.

Ring-barrows are funerary monuments of the Bronze Age, constructed to mark and enclose a burial, though the precise ritual use varied considerably from site to site across Ireland. What survives at Hillgrove includes a bank that reaches a maximum external height of 0.75 metres on its northern side, where a possible causewayed entrance, roughly 1.6 metres wide, can be made out. A causewayed entrance is simply a gap left in the encircling earthworks to allow deliberate access, suggesting the interior was approached in a controlled or ceremonial way. The southern, uphill side of the bank has not survived as well, likely worn away over centuries by the effects of slope and drainage. The monument lies a short distance east of a companion ring-barrow, and the two together suggest this corner of the Iveragh Peninsula was a place of some significance to the communities who shaped it. The site was recorded and described as part of a comprehensive archaeological survey of South Kerry carried out by A. O'Sullivan and J. Sheehan and published by Cork University Press in 1996.