It is horseshoe-shaped, roughly fourteen metres long and twelve metres wide, standing about one and a third metres high, with a four-metre opening facing west. That distinctive shape, and the dark, fire-cracked material packed inside it, identifies it as a fulacht fia, one of the most common yet persistently puzzling monument types in the Irish landscape.

Fulachtaí fia are essentially the remains of ancient cooking sites, or possibly bathing and industrial sites, depending on which archaeological interpretation one favours. The typical method involved heating stones in a fire, then dropping them into a water-filled trough to bring the water to a boil. The cracked, burnt stones were discarded to the sides of the trough over repeated use, gradually building up the characteristic horseshoe mound around it. Thousands of these monuments survive across Ireland, the majority dating to the Bronze Age, roughly 1500 to 500 BC, though some are earlier or later. The placement of this example in low-lying, boggy ground beside a stream is entirely typical; proximity to water was essential, and wetland conditions have helped preserve many of these sites for millennia.

The mound at Kilbarry is described as overgrown, which is the ordinary condition for such sites. The burnt, fragmented stone that constitutes the mound is sometimes called "popcorn stone" by field archaeologists, and once you know what you are looking for, the texture and colouring are distinctive even through vegetation. The western-facing opening, where the trough would originally have been positioned, is still visible at around four metres wide.