It measures twenty metres across and rises only sixty-five centimetres from the surrounding ground, which makes it easy to overlook unless you know what you are looking at. At its centre sits a small stone-lined well, just eighty centimetres in diameter. The combination, a broad spread of burnt material with a water source at its heart, is the defining signature of a fulacht fia.

A fulacht fia is a type of prehistoric cooking or processing site found widely across Ireland and Britain, most commonly dating to the Bronze Age. The typical method involved heating stones in a fire and then dropping them into a trough of water to bring it rapidly to the boil, cooking meat or, as some researchers have argued, serving other purposes such as textile processing or bathing. The stones, cracked and spent from repeated heating and cooling, were discarded nearby, accumulating over time into the characteristic horseshoe-shaped or circular mounds that survive today. The mound at Rossline is composed of exactly this kind of burnt and fragmented stone and charcoal-darkened earth, the physical residue of whatever was being done at the well over many uses and perhaps many generations. The fact that the well survives, stone-lined and still identifiable at the centre of the mound, is a small but satisfying detail; it suggests the site has not been heavily disturbed since it fell out of use.