That waterlogged setting was not incidental. The mound, roughly 17 metres across and about a metre high, was the accumulated debris of a fulacht fia, a type of Bronze Age cooking site found widely across Ireland, where stones were heated in a fire and dropped into a water-filled trough to bring it to the boil. Thousands of such sites survive across the country, recognised by their characteristic crescent shape and dark, fire-cracked stone, but the Fahee example proved unusually well preserved and unusually informative when excavated in 1981.

The excavation, directed by O Drisceoil between June and July of that year, revealed a site more elaborate than its grassy surface had suggested. Inside the enclosing mound were stone-built walls, averaging 1.3 metres wide and about a metre high, which had defined a working area roughly 6 metres in diameter. At the centre lay a rectangular trough, just 2.1 metres by 1 metre and no deeper than 20 centimetres, cut into the subsoil and originally lined with timber planks; the plank slots at each corner survived even where the wood itself had not. About 5 metres to the north-east, a separate stone structure, its large slabs heavily scorched, may have served as a hearth or possibly a roasting oven, though its distance from the trough made the usual interpretation uncertain. A waterlogged pit to the south, filled with burnt stone, deer antler, and bone, may represent an earlier phase of activity before the main trough was constructed. Radiocarbon dating placed the use of the site at around 1400 to 1200 BC. Among the finds recovered were two barbed and tanged arrowheads, a chert scraper, fragments of an amber bead or ring, animal teeth, and further pieces of deer antler, a small material biography of people working and, in some sense, living around this spot during the middle Bronze Age.