They look, at first glance, like unremarkable grassy mounds, but each one marks a site where Bronze Age people repeatedly heated stones in a fire, then dropped them into a water-filled trough to bring it to a boil. The burnt and shattered stones were raked aside after each use, building up over time into the characteristic horseshoe or crescent shape that survives at An Cheathrú Bhán.

This particular example sits in a wet area at the base of a rocky, south-west-facing slope in County Galway, and it is well preserved. The crescent-shaped mound measures roughly 18 metres along its north-east to south-west axis and 14 metres across, opening to the north-west with a gap of about 6 metres. Within that open arc lies the trough itself, approximately 7 metres by 3.5 metres, with a flat base that drains poorly, suggesting the ground here has always held water, which would have made it a practical choice for the site in the first place. A trackway running north-west to south-east clips the south-western edge of the mound, truncating it slightly, while the north-eastern side merges naturally into the slope behind it. What makes the spot particularly interesting is that a second fulacht fia abuts the rear of this one to the south-east, hinting that this wet hollow was returned to repeatedly, perhaps across generations, as a favoured location for whatever activities these structures served.