When it came to light in 1996, land reclamation works had already disturbed the site, leaving a surface spread roughly four metres in diameter of fire-cracked stone and charred debris on the riverbank. Two stone slabs, set upright on their edges, still protruded from the turf at the southern edge of the spread, hinting at some underlying structure. A sunken farm track, cut into the bank to give livestock access to the water, had clipped and truncated the northern side.

The site belongs to a category of prehistoric monument known in Irish as fulachtaí fia, a term for burnt mounds that appear in their thousands across Ireland, particularly near water sources. The prevailing interpretation is that they functioned as outdoor cooking places, where stones were heated in fire and then dropped into a water-filled trough to bring it to the boil. The mounds themselves are the accumulated debris of those shattered, heat-cracked stones, built up over repeated use. What makes the Killeen example particularly interesting is its context: it sits within a linear cluster of such monuments strung along the course of the same stream, with one neighbouring mound lying just fifty metres to the south and another thirty metres to the north. The repetition suggests that this stretch of the Fiddaunglass was returned to, generation after generation, as a working site rather than an incidental one. Whether the three mounds were used simultaneously or represent successive episodes of activity at different points in prehistory is something the surface evidence alone cannot answer.