It is roughly circular, about seven and a half metres across and less than a metre high, and its soil is dark with charcoal. That combination, heat-shattered stone and blackened earth, is the calling card of a burnt mound, a class of prehistoric monument found in considerable numbers across Ireland and Britain. The working theory is that these sites were used for cooking or bathing, perhaps both: stones would be heated in a fire and then dropped into a water-filled trough, bringing it rapidly to the boil. The discarded, fractured stones accumulated over repeated use into exactly the kind of horseshoe or oval mound visible here.

What makes Knocknakilla quietly remarkable is not the single mound but the cluster. Two further burnt mounds lie within close range, one roughly ninety metres to the north-west and another about a hundred and ten metres to the south-west. Finding three such sites in relatively close proximity suggests this was not a casual or one-off activity but something carried out repeatedly, possibly over generations, in a landscape that clearly held some practical or social significance during prehistory. The precise date of use is not recorded for these particular mounds, but burnt mounds in Ireland are generally associated with the Bronze Age, broadly spanning from around 2000 to 500 BC.