What looks like an overgrown hump in a boggy field is, in fact, the surviving remains of a fulacht fia, one of the most common yet least understood monument types in the Irish countryside. The crescent or horseshoe shape is characteristic: it is essentially the accumulated debris of repeated burning, a mound built up over time from thousands of shattered stones discarded after use.

Fulachtaí fia are generally dated to the Bronze Age, though some continued in use into the early medieval period. The working principle was straightforward: stones were heated in a fire, then dropped into a water-filled trough to bring the water to a boil. The thermal shock of repeated heating and quenching cracked the stones, making them useless for reheating, and so they were tossed aside. Over generations of use, this waste material accumulated into the distinctive mound we see today. What the process was actually used for remains debated; cooking is the most widely cited explanation, but brewing, textile processing, and bathing have all been proposed at various times. The example at Curragh retains its opening towards a stream to the south, which would have provided the necessary water supply, and the boggy ground around it is typical of where these sites are found, low-lying, wet, and close to a reliable water source.