A fulacht fia is, in essence, a prehistoric cooking place, typically consisting of a water-filled trough into which heated stones were dropped to bring the liquid to the boil. The burnt and shattered stones, discarded after use, build up into the distinctive horseshoe-shaped mound that survives above ground at many sites across the country.

This particular site was excavated ahead of a large-scale commercial development and turned out to be a well-preserved example. The burnt spread measured roughly 11 metres by 10.5 metres, though it was shallow, reaching a maximum depth of only 0.24 metres. At its centre sat an oval trough, approximately 1.56 metres by 1.44 metres and 0.36 metres deep, which would once have held water. Around the trough, excavators recorded five stake-holes along the southern edge and a sixth at the northern edge, along with two post-holes to the northwest of the site. These small timber fixtures hint at some kind of light structure or working framework built over or around the trough, though exactly what form that took remains open to interpretation. The excavation was reported by Ó Maoldúin and Keeley in 2006.

What makes the Lisnamuck location particularly interesting is that it does not stand alone. A second fulacht fia lies approximately 80 metres to the south. The clustering of these sites, whether coincidental or a sign of repeated, deliberate use of the same landscape over time, is a pattern seen elsewhere in Ireland and adds a small but genuine complexity to what might otherwise seem like an isolated find.