It measures roughly fifteen metres north to south and just over twelve metres east to west, rising only about twenty centimetres at its northern end. That modest rise, barely ankle-height, is what remains of a fulacht fia, one of the most common yet persistently mysterious monument types in the Irish landscape.

A fulacht fia, sometimes called a burnt mound, is the accumulated debris of an ancient cooking method. The standard interpretation is that a trough, dug into the ground and often lined with wood or stone, was filled with water. Stones were heated in a nearby fire and dropped into the trough until the water boiled, at which point meat could be cooked. The cracked, heat-shattered stones were then discarded to the side, building up over repeated use into the horseshoe-shaped or oval spreads that survive today. These sites date most commonly to the Bronze Age, roughly 2000 to 500 BC, though some have returned earlier or later dates. The Cooltomin example sits near the base of a south-west-facing slope in pasture, a setting that is typical of the type; fulachtaí fia are consistently found close to water sources or in low-lying ground where water would have been reliably accessible. The notes compiled by Denis Power record that the western edge of the spread has been cut through by a field drain, which is an unfortunately common fate for low earthworks in agricultural land.

The site is on private farmland, and the mound itself offers little to the untrained eye beyond a darkened spread in the grass and a slight unevenness underfoot. Visitors interested in fulachtaí fia more broadly are better served by reading about excavated examples before visiting an unexcavated one, since the characteristic charcoal-rich, reddish-brown burnt stone is most visible where the soil has been cut or disturbed. Here, the field drain on the western side does expose the mound's profile at its edge, which may offer a clearer view of the burnt material beneath the turf. As with most sites of this kind, the experience is less about spectacle and more about the quiet strangeness of knowing that a patch of ordinary-looking pasture was once, repeatedly, a place of fire and water and organised activity.