The one at Ballahantouragh, in County Kerry, is a quiet example of a type that has puzzled researchers for generations. A fulacht fia typically survives as a horseshoe-shaped mound of fire-cracked stone and dark, charred earth, built up beside a natural water source over repeated episodes of use. The mound forms gradually as spent stone is discarded after each heating, creating an archive of activity in its layers.

The purpose of these sites has been debated since antiquarians first took them seriously. The most widely accepted theory holds that they were cooking places, where stones were heated in a fire and then dropped into a water-filled trough to bring it to the boil. Experiments have shown this works efficiently, and some examples do contain the remains of wooden troughs. Others have been interpreted as saunas, dyeing facilities, or brewing sites, and it is quite possible that different fulachtaí fia served different functions in different periods. Most date to the Bronze Age, roughly 1500 to 500 BC, though some were in use earlier or later. Kerry, with its abundance of wet ground and standing water, is particularly rich in them. Ballahantouragh sits within a landscape that would have supported exactly the kind of marginal, seasonal activity these sites seem to represent, places used periodically rather than permanently settled.