What makes this particular example notable is not just its age but its complexity. Beneath a low, sub-oval mound of burnt sandstone measuring twelve metres north to south and just under a metre deep, excavators found not one trough but three, cut into the ground at different times and overlapping one another, suggesting a place that people returned to repeatedly over a long period.

The excavation, carried out by Emer Dennehy under licence reference 02E0849, revealed three distinct phases of activity. A fulacht fia works on a straightforward principle: a trough is filled with water, stones are heated in a nearby hearth until red-hot, then dropped into the trough to bring the water to a boil, producing a pile of cracked, fire-shattered stone, the burnt mound itself. At Leahys, Phase I involved a rectangular trough some 3.5 metres long, associated with a small hearth and a sandstone revetment, a low retaining wall, along the northern edge to hold back the growing mound material. Phase II introduced a smaller, roughly circular trough paired with a substantially larger hearth, and the remains of a pot-boiler, a shallow stone-lined basin likely used to heat smaller volumes of liquid. By Phase III, the earlier features had been abandoned and backfilled, and a new sub-oval trough, nearly 2.7 metres across and 0.6 metres deep, was cut directly over a natural spring. When the site was finally abandoned, this last trough was left open, and the spring water welling up in its base created the waterlogged, oxygen-poor conditions in which peat slowly accumulated. A small bone fragment came from the Phase II trough, and a pollen core was extracted from the peat in Phase III, though no other artefacts were recovered.

The site is not formally presented for visitors and there are no facilities on the ground. The excavation record, compiled by Denis Power and uploaded to excavations.ie in August 2012, is the primary accessible source for anyone wanting to read the full technical detail. The pollen core taken from the Phase III peat holds the best chance of eventually yielding environmental data about what the landscape around Leahys looked like when the fires were last lit and the stones last cracked.