The example at Lisduff in County Longford is a quiet case in point: a low, horseshoe-shaped mound of earth and stone sitting on a north-facing slope in rough pasture, measuring roughly ten metres north to south and seven metres east to west, rising no more than half a metre at its highest. Its opening faces south-west, and fragments of burnt stone are still visible within it, the residue of repeated heating and quenching that defines this monument type.

A fulacht fia, broadly speaking, is thought to be a prehistoric cooking or processing site. The typical arrangement involved a trough dug into the ground near a water source, which would be filled with water and then heated by dropping fire-cracked stones into it. Those stones, once spent, were discarded to the sides and rear, and over time the accumulation of cracked and blackened material built up into the characteristic horseshoe form that survives today. At Lisduff, the logic of the site is still legible in the landscape: the bed of a stream can be traced a short distance to the east, almost certainly the water source that made the location practical in the first place. Most fulachtaí fia date to the Bronze Age, roughly 2000 to 500 BC, though some sites show evidence of use across longer periods. The monument at Lisduff has not been excavated, so the precise chronology here remains unknown.