It is, in fact, the remains of a fulacht fia, one of the most common yet consistently puzzling monument types in the Irish landscape. These are burnt mounds, the accumulated debris of a Bronze Age cooking method in which stones were heated in a fire and then dropped into a water-filled trough to bring it to the boil. Over repeated use, the cracked and spent stones were raked out and piled beside the trough, building up over time into the horseshoe or oval shapes that survive today in their thousands across Ireland.

The Glansheskin example is a well-preserved specimen of the type. The mound itself is oval, measuring roughly 23 metres on its north-east to south-west axis and 16 metres across, rising to a height of about 1.45 metres, which is considerable for a monument that began simply as a pile of discarded, fire-shattered stone. At its south-eastern side, a shallow depression, approximately six metres across and half a metre deep, marks where the trough once sat. The proximity to the stream would have been no accident; a reliable water source was essential to the whole operation, and fulachtaí fia are almost invariably found close to rivers, streams, or boggy ground. Whether the site was used primarily for cooking, as the traditional interpretation holds, or for other purposes such as bathing, textile processing, or brewing, remains a matter of ongoing debate among archaeologists.