By the time surveyors arrived, the mound was gone, but the evidence it had left in the ground was still legible: dark burnt soil and heat-shattered red stone showing through the grass, spread across an area roughly thirteen metres from north to south and twelve from east to west.

A fulacht fia is a type of Bronze Age cooking monument found in enormous numbers across Ireland, typically comprising a horseshoe-shaped mound of fire-cracked stone beside a trough and a water source. The standard interpretation is that stones were heated in a fire and then dropped into a water-filled pit to bring it to the boil, cooking meat or, as some researchers have argued, other materials entirely. The Knockawinna example followed the pattern closely: a well lies just to the northwest of the site, and the mound itself had stood, according to the landowner, to a height of between five and six feet, somewhere between 1.5 and 1.8 metres. That is a substantial accumulation, suggesting repeated use over a long period. The Castleisland District Archaeological Survey recorded what remained in 1985, noting that the spread of burnt material was bordered by a dyke on the eastern side.