The typical site consists of a horseshoe-shaped mound of fire-cracked stone, usually surrounding a waterlogged hollow or trough, found most often in low-lying, marshy ground. The prevailing interpretation is that they were cooking sites, where stones were heated in a fire and then dropped into a water-filled trough to bring it to the boil, with dates clustering broadly in the Bronze Age, roughly 1500 to 500 BC. The one at Treanrevagh, in County Mayo, is one such site, sitting quietly in a part of the west of Ireland where this kind of monument is far from uncommon, though no less worth pausing over for that.

The mechanics of a fulacht fia are straightforward enough, which is part of what makes the sheer number of them so striking. Repeated heating and rapid cooling causes stone to fracture, and the characteristic shattered, reddened rubble that builds up around the trough over many uses is precisely what survives and what makes these sites identifiable today. Some researchers have proposed alternative functions, including brewing or textile processing, though cooking remains the most widely accepted explanation. The Treanrevagh example sits within a broader Mayo landscape that preserves considerable evidence of prehistoric activity, though the particular details of this individual site, its dimensions, its state of preservation, and any associated finds, are not currently in the public record.