The one at Clenagh, in County Clare, is a quiet example of a site type that has puzzled researchers for generations. A fulacht fia typically survives as a horseshoe-shaped mound of burnt and shattered stone, usually found close to a water source, and dating broadly to the Bronze Age. The stones were heated in a fire and then dropped into a water-filled trough to bring the water to a boil, a process that gradually produces the characteristic crescent of discarded, fire-cracked material that marks these sites today.

What exactly these sites were used for remains genuinely contested. The most widely accepted theory is that they functioned as cooking places, perhaps for communal feasting or for groups of hunters and travellers. Experimental archaeology has shown that a fulacht fia trough can boil a large volume of water surprisingly quickly using this method. Other proposals have included use for brewing, fabric dyeing, or bathing, and it is possible that different sites served different purposes at different times. The Clenagh example sits within a county that has a notable concentration of prehistoric monuments, a reflection of how densely settled and actively worked the Clare landscape was during the Bronze Age, roughly 2000 to 500 BC.