This is a fulacht fia, a type of prehistoric cooking site found in enormous numbers across Ireland, typically Bronze Age in date. The usual interpretation is that stones were heated in a fire and then dropped into a water-filled trough to bring the water to a boil, a method that leaves behind exactly this kind of spread: a horseshoe or oval mound of shattered, heat-reddened stone, often with a hollow at its centre where the trough once sat.

The mound at Knockahorrea measures roughly 21 metres north to south and just under 18 metres east to west, which places it at a considerable size for this type of monument. It still stands to about 0.58 metres in height, though local knowledge records that it was once significantly higher before drainage works around 1984 levelled much of it. During those works, a drain was cut directly through the centre of the mound, removing material and leaving behind the central depression that is still visible today, measuring roughly 7.6 metres by 4.2 metres and dropping to around 0.22 metres below the surrounding surface. That hollow almost certainly marks where the original trough or pit was located, the functional core of the site around which generations of burnt stone gradually accumulated.

The 1984 intervention is a reminder of how frequently these monuments have been diminished by agricultural improvement over the centuries, often without any awareness of what was being altered. What survives at Knockahorrea is a reduced but still legible version of a feature that, in its original form, would have been a more conspicuous presence in the landscape.