It is not a burial cairn or a field boundary; it is the remnant of a fulacht fia, a type of prehistoric cooking or processing site found in their thousands across Ireland, typically dating to the Bronze Age. The characteristic shape comes from the accumulated debris of fire-cracked stone, the waste product of a process in which rocks were heated and then plunged into a water-filled trough to bring it to the boil.

The mound at Knockahorrea measures roughly 16.7 metres along its northeast to southwest axis and 13.4 metres across, dimensions that place it among the more substantial surviving examples of its type. The opening, about two metres wide, faces northwest, which is typical of fulachta fiadh generally, though the reasons for consistent orientation are still debated by researchers. Material has been removed from the eastern and southern sides of the mound at some point, whether through deliberate quarrying of the burnt stone, agricultural disturbance, or simple erosion over the centuries is not recorded. What remains gives a clear enough impression of the original form: a crescent of dark, fire-blackened stone enclosing a hollow where the trough would once have sat, positioned close to the stream that would have supplied the water essential to the whole operation.