It measures roughly twenty-two metres long, twelve metres wide, and less than a metre high, with a slight hollow pressed into its northern face. That hollow is the clue to what this mound actually is: the accumulated debris of a fulacht fia, a type of prehistoric cooking site found in their thousands across Ireland, typically beside water and in low-lying, boggy ground.

A fulacht fia, sometimes called a burnt mound, generally consists of a trough dug into the earth, filled with water, and heated by dropping fire-cracked stones into it. The stones, once spent, were raked out and discarded nearby, building up over repeated use into exactly the kind of horseshoe or semicircular mound visible at Ballynamona. The practice is associated with the Bronze Age, though some sites were used across long periods, and the precise purposes, cooking, bathing, textile processing, or some combination, remain a subject of genuine debate among archaeologists. What makes the Ballynamona example quietly interesting beyond its form is its immediate landscape: it sits in marshy ground just to the north-east of a stream, precisely the wet, marginal terrain these sites consistently favour, and roughly two hundred metres to the north-north-west lies a holy well, a proximity that may be coincidental but is the kind of detail that lingers.