A small annotation on an Ordnance Survey six-inch map, made by a T. Coffey, reads simply: "Small amount of burnt stone. Site of destroyed fulacht fia." That is the entirety of the physical evidence that survived.

A fulacht fia is a type of prehistoric cooking site found in enormous numbers across Ireland, typically identified by a horseshoe-shaped mound of fire-cracked stone beside a water source. The method involved heating stones in a fire and dropping them into a water-filled trough to bring it to a boil, leaving behind the shattered, heat-reddened debris that forms the characteristic mound. Here at Gleninagh, the thin soil cover on a narrow, level shelf of ground offered a natural setting for such activity, and a natural spring lies approximately twenty metres to the north. By the time the site was formally listed in the Sites and Monuments Record in 1992 and the Record of Monuments and Places in 1996, whatever mound had once existed was already gone. The burnt stone noted by Coffey had evidently been cleared or dispersed at some earlier point, likely during agricultural activity on the same marginal ground.

The spring to the north is a more tangible presence. It is enclosed within a 19th-century gothic well-house, a small architectural curiosity that frames a natural water source in the ornamental style fashionable among estate builders of that period. The proximity of the well-house to the vanished fulacht fia is a quiet coincidence, the same spring that may once have supplied prehistoric activity later dressed up in Victorian stonework.