When it was identified in 1995, it took the form of a roughly oval peat-covered mound, approximately eight metres north to south, six metres east to west, and standing around 0.7 metres high, sitting on a boggy, north-facing slope within a young coniferous forest. The material it was made of, heat-shattered stones mixed through charcoal-enriched soil, is the defining signature of a burnt mound.

Burnt mounds are among the most common prehistoric monument types in Ireland, though their precise function remains debated. The leading theory is that they represent cooking sites, where stones were repeatedly heated in fire and dropped into water-filled troughs to bring the water to the boil, a method that leaves behind exactly this kind of cracked, fire-fractured rubble. They date most commonly to the Bronze Age. The Knocknakilla example had been cut by two drainage channels before it was first recorded, which likely accelerated whatever processes were already working against its survival. By the time anyone returned to check, the mound had gone, absorbed back into the boggy ground or dispersed by forestry activity.