Nothing about the surface would have suggested it. Only the routing of a Bord Gáis Éireann pipeline, the Hollybrook-Wicklow line, and the monitoring of the topsoil-stripping that came with it, brought the site to light. Beneath the turf lay the remnants of a fulacht fia, a type of prehistoric cooking or industrial site found in great numbers across Ireland, typically characterised by a mound of fire-cracked stone beside a water source and a trough used for heating water by dropping in stones heated in a fire.

The Kilmartin site occupied a low, sheltered valley where a small unnamed stream once ran north-west to south-east, though by the late twentieth century even that had been buried in a pipe. Once excavators hand-cleaned an area of roughly 15.5 metres by 7 metres, they found spreads of heat-shattered stone and charcoal, the classic signature of a fulacht fia, along with something rather more precise: a timber-lined trough. It was a shallow rectangular cut, 2.19 metres long and just under a metre wide, with two substantial split oak planks surviving at its base in waterlogged condition. The northernmost plank measured 1.78 metres; the southernmost, 2.08 metres. Neither showed tool-marks. Around the corners of the trough, two clusters of eight stake-holes each were recorded, suggesting paired corner posts that may once have supported some kind of structure over the working area. To the west lay a large pit, 3.3 metres by 1.8 metres and 0.8 metres deep, filled with several layers of silty clay and occasional lenses of heat-shattered stone. The burnt mound material itself survived in two spreads, one to the south-west and a larger one to the north, both thin but clearly prehistoric in origin, overlying natural boulder clay and the old gravels of the former stream bed. The shape of the southern spread had been distorted over time by repeated episodes of land improvement, the ordinary agricultural work of centuries quietly pressing down on something much older.