The one at Keelhilla, in County Clare, is a quiet example of a type that still provokes genuine debate among archaeologists. A fulacht fia typically survives as a horseshoe-shaped mound of fire-cracked stone and dark, charred soil, the accumulated debris of repeated heating episodes that may span centuries. Water was brought to a trough, usually timber-lined or cut into the ground, and stones heated in a nearby fire were dropped in to bring it to the boil. What exactly the water was used for, whether cooking, bathing, textile processing, or brewing, remains an open question, and probably the answer varied from site to site and era to era.

Most fulachtaí fia date to the Bronze Age, roughly 2000 to 500 BC, though some sites show evidence of use into the early medieval period. They are almost always found near water, beside streams, springs, or boggy ground, which reflects the practical requirement for a reliable water source. County Clare has a significant concentration of them, spread across its varied terrain of limestone pavement, bogland, and river valley. The Keelhilla example sits within this broader pattern, one node in a network of prehistoric activity that the modern landscape has largely absorbed and obscured.