The one at Ballykilty in County Clare is typical in that respect: a low, horseshoe-shaped mound of fire-cracked stone, dark soil, and charcoal, sitting quietly in the landscape with little to announce what it once was. These mounds are the debris of repeated heating, the accumulated by-product of an ancient process in which stones were fired in a hearth and then dropped into a water-filled trough, bringing the water rapidly to the boil. Whether the troughs were used for cooking, bathing, textile processing, or some combination of all three remains a matter of genuine archaeological debate.

Fulachtaí fia are generally dated to the Bronze Age, roughly 1500 to 500 BC, though some examples have returned earlier or later dates. They tend to cluster near streams or marshy ground, a practical necessity given the volume of water the process required, and Ballykilty, like most of Clare, has the kind of low-lying, water-retentive terrain that seems to have suited this activity well. The sheer number of these sites across Ireland, estimated at over four thousand recorded examples, suggests they were not occasional or ceremonial features but something closer to a routine part of daily or seasonal life.