A fulacht fia is, in essence, a Bronze Age cooking site, consisting of a trough for heating water using fire-cracked stones, which were repeatedly heated and plunged into the water. The broken, burnt stones were then discarded nearby, forming the characteristic mound that survives. At Greenhill, that mound measures roughly twenty metres north to south and eighteen metres east to west, a considerable spread sitting about twenty metres north of a local well.

What makes this particular site quietly telling is what happened to it before anyone thought to record it formally. Local information indicates that the mound was once significantly larger, and that material was removed from it to serve as road metalling, the practice of using broken stone and rubble to surface or repair roads. It was a fate shared by a great many earthworks across rural Ireland, where prehistoric monuments were treated as a convenient source of fill or hardcore. The Bronze Age deposits at Greenhill, built up over repeated episodes of cooking or possibly other communal activity, were gradually carted away and pressed flat beneath traffic. What remains is the residue, a grass-covered shadow of the original accumulation.