Two large spreads of burnt mound material, blackened and heat-fractured stone mixed with charcoal-rich soil, stretched along the riverbank, with two substantial trough features and a scattering of pits and stake-holes lying between them. It is an unglamorous kind of site, but burnt mounds are among the most intriguing and debated monument types in Irish prehistory.

A burnt mound, sometimes called a fulacht fiadh, typically consists of the accumulated waste from a process involving fire and water. The general working theory is that stones were heated in a fire and then dropped into a water-filled trough, a wooden or stone-lined pit, to bring the water rapidly to the boil. The shattered, spent stones were then raked aside, building up the characteristic mounded deposits over repeated use. What exactly these sites were used for, whether cooking, bathing, textile processing, or something else entirely, remains an open question. The Ballybeg example, excavated under licence number 02E0542 and reported by Bennett in 2004, fits the classic riverside pattern well: water would have been readily accessible from the Rathnew River, and the two troughs suggest the site saw sustained or repeated activity rather than a single episode of use. The presence of stake-holes hints at some form of wooden structure associated with the workings, though their precise function is unclear.