It measures roughly ten metres north to south, about eight metres east to west, and rises just 0.7 metres above the surrounding ground. To a passing eye it might read as a slight irregularity in the field, perhaps a collapsed wall or a natural rise. It is, in fact, the remains of a fulacht fia, the distinctive burnt-mound sites found in their thousands across Ireland, most of them dating to the Bronze Age.

A fulacht fia typically consists of the debris left behind by repeated episodes of fire-cracking stones. The method involved heating stones in a fire and dropping them into a water-filled trough to bring the water to a boil, after which the cracked and spent stones were discarded to the side. Over generations of use, these discarded stones accumulated into the horseshoe or semicircular mounds that survive today. The precise purpose, whether cooking, bathing, textile processing, or some combination, remains a matter of ongoing debate among archaeologists. The Glenleigh example fits the classic profile: a burnt-stone mound of modest height in low-lying ground, the kind of setting that would once have offered reliable access to water. What distinguishes its present condition is the recent trackway that now cuts across the western half of the mound, a mundane modern intrusion into a feature that had otherwise quietly endured for millennia.