The most striking of these was a fulacht fia, the term used for a prehistoric burnt mound, essentially the accumulated debris of a cooking or industrial process in which stones were heated in fire and then plunged into a water-filled trough to bring it to the boil. The mound at Ballyhenry is a substantial one, roughly 25 metres long, 15 metres wide, and about a metre deep, built up over time from the cracked and fire-shattered stones discarded after each use.

The finds came to light during test-trenching carried out in the townland of Ballyhenry as part of pre-development archaeological work in advance of the proposed N11 Wicklow Bypass road improvement scheme. Within that 0.5 kilometre corridor, four distinct areas of archaeological potential were identified. Around 20 metres north of the main mound, a second spread of burnt mound material survived, roughly 7 metres in diameter. Further north still, a third deposit appeared as a smaller spread, possibly associated with a pit, with a dump of apparently unburnt stone lying beside it. A fourth area, at the southernmost end of the test corridor, was different in character: two parallel ditches with an area of burning between them and a large pit nearby, suggesting a different kind of activity altogether, though one still involving deliberate use of fire. The clustering of these features across a relatively short distance points to a landscape that was returned to, and worked in, across considerable stretches of time.