They appear as low, horseshoe-shaped mounds, typically found near water, and are thought to date mostly from the Bronze Age, roughly 1500 to 500 BC. The working theory is that they were cooking sites: stones were heated in a fire, then dropped into a water-filled trough to bring it to a boil, and the cracked, heat-shattered stones were piled to the side over time, forming the distinctive mound that survives today. Some researchers have argued for alternative uses, including textile processing or bathing, but the cooking interpretation remains the most widely accepted. The example at Levallinree, in County Mayo, is one such site, quietly occupying a corner of the landscape with little to distinguish it at first glance from the surrounding terrain.

Mayo has a notable density of Bronze Age activity, and fulachtaí fia turn up with some regularity across its boggy lowlands and river margins. The waterlogged conditions that make much of the county agriculturally awkward are precisely the conditions that tend to preserve these monuments, keeping the organic material within the troughs intact for millennia. Levallinree itself is a townland in the west of Ireland where this kind of low-lying, wet ground is common, and the placement of a fulacht fia there follows the pattern seen at similar sites elsewhere: proximity to a reliable water source, away from settlement but not so remote as to be impractical for repeated use.