It is barely half a metre high at its tallest point, elongated in a rough semicircle, and covered in ordinary turf. But beneath that sod lies a layer of black soil packed over a dense concentration of fire-cracked stone, and that combination is the signature of a burnt mound, one of the most common yet least understood monument types in the Irish landscape.

Burnt mounds, sometimes called fulachtaí fia in Irish, are the accumulated debris of repeated high-temperature activity, most likely cooking or industrial heat processes, carried out over centuries during the Bronze Age. The method typically involved heating stones in a fire and dropping them into a water-filled trough to bring the water rapidly to the boil. The stones, unable to withstand the thermal shock, shatter and blacken, and are then discarded in a crescentric heap around the working area. Over time, that heap becomes a mound. The example at Robeenard follows the pattern precisely in its placement as well as its composition. It sits at the interface between the wet, marshy floor of the valley and the drier rising ground to the north, a location that would have given prehistoric users reliable access to standing water without the inconvenience of working in the bog itself. A field drain now runs along the mound's straight northern edge, dry and grass-grown, though its original course may well have followed a natural watercourse that made the spot attractive in the first place. The mound measures 14.7 metres east to west and 5.6 metres north to south, modest in scale but consistent with the hundreds of similar features recorded across Ireland's wetter western counties.