It measures roughly eight metres across in either direction and barely half a metre in height, irregularly shaped and easy to miss. What it represents, however, is a type of site found across Ireland and Britain in considerable numbers, and one whose precise purpose has kept archaeologists arguing for decades.

Burnt mounds, sometimes called fulacht fiadh in the Irish tradition, are among the most common prehistoric monuments in the Irish landscape. They tend to cluster near water, which is exactly the case here at Killalough, and they are composed of the accumulated debris of repeated heating: stones cracked by thermal shock and soil darkened by charcoal. The working theory is that stones were heated in a fire, then dropped into a water-filled trough to bring it rapidly to the boil. What the boiling water was used for is less certain. Cooking meat is the long-standing interpretation, but proposals have ranged from textile processing and leather-working to communal bathing. The typical Bronze Age date for these sites, roughly 1500 to 500 BC, is well established through radiocarbon dating at comparable sites, though no such testing is recorded for this particular mound. The location at a stream confluence would have given reliable, year-round access to flowing water, which was essential to whatever process was taking place.