It left no trace on the surface. Had a drainage scheme not cut through the ground in 2006, it would quite possibly have remained invisible indefinitely.

What the soil stripping revealed was a fulacht fia, a type of prehistoric cooking or processing site found widely across Ireland and Britain. The typical arrangement involves heating stones in a fire until they are intensely hot, then dropping them into a water-filled trough to bring it rapidly to the boil. Over time, the spent, shattered stones accumulate into a characteristic horseshoe-shaped mound. At Farrannoo, the mound had been disturbed at some point before excavation, leaving two separate concentrations of burnt stone, ash, and charcoal rather than a single intact spread. The larger concentration measured roughly 5.2 by 5.8 metres; the smaller lay about a metre to the south. At the western edge of the larger deposit, excavators found the trough itself, oval in plan, about 3.2 metres long and a metre wide, with a flat base and near-vertical sides. Crucially, a single oak plank, split tangentially from its parent timber and measuring 2.7 metres in length, was still lying in situ along the base of the trough, a rare survival of the wooden lining that would have made the trough watertight. A separate cylindrical pit, uncovered beneath the smaller stone spread, had a shallow channel cut along its northern edge, apparently designed to direct water into it. Among the finds recovered were a retouched chert blade, flint debitage left over from toolmaking, and fragments of animal bone. A second fulacht fia was excavated just 35 metres to the north, suggesting this low, reed-fringed ground beside a small stream was a place people returned to repeatedly, for reasons that remain, as with so many of these sites, genuinely uncertain.