It measures roughly four metres east to west and three metres north to south, and beneath the turf lies a spread of burnt material that marks it out as a fulacht fia, one of the most common yet persistently mysterious monument types in the Irish landscape.

Fulachtaí fia, found in their thousands across Ireland, are the remnants of ancient cooking or processing sites, typically dating to the Bronze Age. The standard interpretation holds that they functioned as outdoor boiling troughs: a pit lined with timber or stone would be filled with water, and fire-heated rocks dropped in to bring it to temperature. Over time, those rocks cracked and shattered with repeated heating and cooling, and the resulting mounds of dark, burnt stone and charcoal accumulated around the trough. The preference for low-lying, wet ground near water, as at Cloonteens, is entirely characteristic; proximity to a stream provided a ready water supply, and the boggy surroundings helped preserve the organic material. Some researchers have proposed alternative uses, from textile processing to sweat houses, and the debate has never been fully settled.