It is not particularly dramatic to look at, roughly semicircular, about ten metres across and less than two metres high. But this modest heap of scorched and shattered stone is a fulacht fia, one of the most common prehistoric monuments in Ireland, and one that raises questions archaeologists are still working to settle.

A fulacht fia is the remains of an ancient outdoor cooking site, typically Bronze Age in date, though some examples are older or younger. The method was straightforward: stones were heated in a fire, then dropped into a water-filled trough, bringing the water rapidly to a boil. The stones cracked and spalled with the repeated thermal shock, and the discarded fragments accumulated over time into the characteristic horseshoe or kidney-shaped mound that survives today. At Rockhill, that mound measures ten metres on its north-west to south-east axis and six metres on the other, with a height of 1.7 metres, which suggests sustained and repeated use of the site over a considerable period. The placement is typical: fulachtaí fia are almost always found near water, and this one sits on the north-west side of a stream, with the ground sloping away to overlook the valley below. One detail here is slightly unusual: the north-east side of the mound is straight-sided and appears to have been recently cut, with burnt material spreading about four metres outward in that direction, suggesting the mound has been disturbed at some point, possibly by agricultural work or a drainage scheme.