At Knockbaun in County Mayo, one such site sits quietly in the landscape, a low horseshoe-shaped mound of fire-cracked stone that represents a technology used repeatedly across the Bronze Age, roughly between 1500 and 500 BC.

The typical fulacht fia consists of a burnt mound, the accumulated debris of countless heating sessions, alongside a trough dug into the ground and lined with wood or stone. The method was straightforward: stones were heated in a fire, then dropped into a water-filled trough, bringing the water rapidly to a boil. What exactly this process was used for has been debated for decades. Cooking meat is the most widely accepted explanation, supported by experimental archaeology, but proposals have included textile processing, bathing, and even the production of ale. The sheer number of these sites across Ireland suggests they were a routine feature of Bronze Age life rather than anything ceremonial or specialised. Mayo has a particularly dense concentration of them, partly because the county retains large areas of blanket bog that have preserved low-lying earthworks which might have been lost elsewhere to centuries of ploughing and development.

The Knockbaun example is one of many such monuments recorded across the county, its precise details not yet fully documented in publicly available sources. What is known is the type: a monument class that connects this quiet Mayo townland to a pattern of prehistoric activity stretching the length and breadth of the island.