They appear as low, horseshoe-shaped mounds, typically dark with charred and fire-cracked stone, and they cluster near water. The one recorded at Gortaganniv, in County Clare, is one of countless such sites that punctuate the Irish midlands and west, each marking a place where people once heated water by dropping fire-heated stones into a trough or pit.

The mechanism itself is straightforward and has been convincingly demonstrated by modern experiments: stones heated in a fire and dropped into a water-filled trough bring the water to a boil surprisingly quickly, and keep it there with fresh stones as needed. What is less settled is what exactly the water was for. Cooking is the most widely accepted explanation, with Bronze Age communities using these sites to prepare food, likely meat, over the course of perhaps two or three thousand years before and around the middle of the second millennium BC. Other theories, supported by some experimental archaeology, propose uses ranging from bathing to textile production. The mound itself is the accumulated debris of the process, generations of spent, shattered stone discarded in a crescent around the working area. At Gortaganniv, the site sits within a townland whose Irish name suggests a small, enclosed agricultural landscape, the kind of low-lying ground near seasonal water that fulachtaí fia consistently favour.