They appear as low, horseshoe-shaped mounds, typically found near water, and are associated with the Bronze Age practice of heating stones in a fire and dropping them into a water-filled trough to bring the water to a boil. What they were actually used for, whether cooking, bathing, textile processing, or something else entirely, remains a matter of genuine debate among archaeologists. The example recorded near Cashel in County Mayo is one of many such sites that punctuate the boggy, lake-edged terrain of the west of Ireland, places where the waterlogged ground has preserved the burnt and shattered stone that gives these monuments their character.

The term fulacht fia is an Old Irish phrase sometimes translated loosely as "cooking place of the deer" or "cooking place of the wild", though the precise meaning has been disputed. The burnt mounds that survive today are essentially the accumulated spoil of repeated use, cracked stones discarded after each heating cycle building up over time into the low earthworks visible across the countryside. In Mayo, where bogland has historically covered large areas and provided excellent preservation conditions, Bronze Age activity of this kind is well attested, and such sites form part of a broader pattern of prehistoric settlement and land use that stretched across the province during the second and early first millennia BC.