Beneath a thin layer of soil near Easton, between Celbridge and Leixlip in County Kildare, lay a flat scatter of heat-fractured stone that had been quietly waiting for several thousand years. Its discoverers were not archaeologists with trowels and a hunch, but engineers stripping topsoil for a road interchange. What they uncovered was a fulacht fia, a type of prehistoric cooking or processing site found in great numbers across Ireland, typically consisting of a mound of fire-cracked stones accumulated beside a water trough. These sites are thought to date mainly from the Bronze Age, and were formed by heating stones in a fire and dropping them into a water-filled pit to bring it to the boil.

Monitoring of the Celbridge Interchange scheme, which ran for approximately four kilometres through gently undulating land with a mixture of arable, pasture and woodland, took place between April and December 2001 under licence number 01E0306. The scheme also passed through a landscape shaped by eighteenth-century design, with avenues and tree-lined field boundaries belonging to Castletown, the early eighteenth-century house nearby. Designated Site 15 during the works, this particular fulacht fia measured fourteen metres by four and a half metres before excavation. Once the spread of fractured stone was removed, it revealed four rectangular troughs, two pits, five post-holes, and twenty-one stake-holes, with most of the stake-holes concentrated along the southern edge. The site had not survived entirely intact. A post-medieval boundary ditch had cut across it on a north-east to south-west alignment, and a modern water pipe crossed its northern edge, both intrusions serving as a reminder of how many layers of activity can compress into a single patch of ground. The stone spread itself was only between five and ten centimetres thick, yet it had been enough to seal the features beneath it for centuries.