These low, horseshoe-shaped mounds of burnt and shattered stone are found beside streams and boggy ground throughout the country, and they represent a technology that was in use for well over a thousand years during the Bronze Age. What exactly they were for remains a matter of debate among archaeologists, though the dominant interpretation is that they functioned as cooking sites: stones were heated in a fire, then dropped into a water-filled trough to bring it to the boil rapidly. Experiments have confirmed this works efficiently, and a modest joint of meat can be cooked in the time the method suggests.

The characteristic crescent shape of these mounds is itself a byproduct of the process. Each time stones were used, they cracked and became useless for further heating, and so they were tossed aside around the edge of the trough. Over repeated use across seasons or generations, this discarded material built up into the low banks that survive today. The sites tend to cluster near water, both because a reliable supply was essential to the process and because low-lying, boggy ground preserved the organic material within the troughs, sometimes including the wooden lining itself. County Mayo, with its blanket bogs and numerous watercourses, contains a considerable concentration of these monuments. The site at Cunnagher is one of many in the region that speak to sustained Bronze Age activity across what is now a quiet rural landscape.