The one at Lissanair, in County Clare, is a quiet example of a site type that has puzzled and fascinated researchers for generations. A fulacht fia typically appears as a horseshoe-shaped or kidney-shaped mound of fire-cracked stone, usually found close to a water source. The working theory, broadly accepted today, is that these were cooking sites: stones were heated in a fire, dropped into a water-filled trough to bring it rapidly to the boil, and used to cook meat. Experiments have shown the method works remarkably well. Most date to the Bronze Age, roughly 1500 to 500 BC, though some are earlier or later.

The Lissanair site sits within a county that has no shortage of prehistoric remains, from the limestone pavements of the Burren with their wedge tombs and portal dolmens to the ringforts and souterrains of the lowlands. Clare's landscape, with its abundance of springs, boggy hollows, and slow-moving streams, provided exactly the wet conditions that fulachtaí fia seem to require. The mounds survive because the shattered, heat-fractured stone of which they are composed was of little practical use to later farmers, who were generally happy to leave them alone. That indifference, as much as anything else, is why so many have endured.