Beneath the turf lies a spread of burnt and fire-cracked stone, the signature remains of a fulacht fia, a type of prehistoric cooking site found in considerable numbers across Ireland. The typical fulacht fia consisted of a trough, often timber-lined or cut into the ground, filled with water that was heated by dropping fire-heated stones into it. The shattered, blackened stone that accumulated from repeated use is what survives most readily, forming the characteristic horseshoe-shaped mounds that archaeologists have come to recognise across the Irish landscape.

The site at Castleblagh was recorded by Lee in 1932, who placed it approximately 150 yards south of a nearby rath, the circular earthwork enclosure common throughout early medieval Ireland. That spatial relationship is worth noting. Fulachtaí fia are generally understood to be prehistoric in origin, most dating to the Bronze Age, though the proximity to a rath raises quiet questions about how long a particular patch of ground might remain in active or remembered use across different periods. The mound sits in ordinary farmland now, doing nothing to announce itself.