Beneath the turf lies a spread of burnt material, the compacted residue of a fulacht fia, one of the most common yet least understood monument types in the Irish landscape. These are the remains of prehistoric cooking sites, typically Bronze Age, where stones were heated in fire and then dropped into water-filled troughs to bring the water to boiling point. The process left behind great quantities of cracked, fire-shattered stone, and over centuries these dumps accumulated into the characteristic horseshoe-shaped or rounded mounds that dot Irish fields in their thousands.

What makes the Knocknageeha example worth pausing over is the specific detail recorded by a Broker in 1937, who measured it as roughly round, about four spades across, which he estimated at around twenty-two feet in diameter, and standing four feet high. That is a reasonably substantial mound, suggesting repeated and sustained use of the site over time. The mound has since been cut through by narrow drainage channels, set about two metres apart, which have exposed the interior spread of burnt material but also inevitably disturbed the archaeology. The surrounding land remains in agricultural use as pasture, and the mound itself is grass-covered, giving little outward sign of what lies beneath.