It measures nearly fifteen metres at its longest and rises just over a metre above the surrounding ground. To pass it without knowing what it was, you might take it for a natural rise or a collapsed field boundary. It is neither. It is a fulacht fia, one of the most common prehistoric monument types in Ireland, and one of the least understood.

A fulacht fia, sometimes called a burnt mound, is the accumulated debris of repeated episodes of water-heating using fire-cracked stone. The typical interpretation is that stones were heated in a fire, then dropped into a water-filled trough, bringing the water rapidly to a boil. Whatever the trough was used for, whether cooking, processing hides, or something else entirely, the cracked and spent stones were raked out and piled beside it after each use, building up over time into the low, horseshoe-shaped or oval mounds that survive today across the Irish landscape. The proximity of this example to a stream is entirely characteristic; a reliable water source was a practical necessity. The site at Keeltane follows the pattern closely, sitting just far enough from the water to stay clear of flooding while remaining convenient to it. Unfortunately, parts of the mound on its southern and western sides have been removed at some point, reducing what was once a more complete monument.