It measures roughly twelve metres along its longer axis and rises only half a metre from the surrounding pasture, yet what lies beneath that modest profile is a dense accumulation of heat-shattered stones packed into black, charcoal-rich soil. This is a fulacht fia, a type of prehistoric cooking site found in extraordinary numbers across Ireland, typically Bronze Age in origin, and this one retains what is almost certainly the hollow where the central trough once sat: a shallow depression, about two metres wide, nestled between the inner arms of the horseshoe at the south-south-east.

The mechanics of a fulacht fia were straightforward but effective. Stones would be heated in a fire and then dropped into a water-filled trough, bringing the water to a boil and allowing large cuts of meat to be cooked. The stones, cracked and spent from repeated thermal shock, were discarded to the sides, and over generations of use these deposits built up into the characteristic mound shape that survives today. The site at Corbally sits in a natural depression of wet ground with a stream just ten metres to the south-south-east, the kind of reliable, accessible water source that made such spots attractive to prehistoric communities in the first place. The mound stands out precisely because it is not the surrounding landscape: everything around it is soft and waterlogged, while the compacted stone debris beneath holds its shape and drains well enough to feel almost anomalous underfoot. A second fulacht fia lies approximately 120 metres to the north-north-east, which suggests this particular corner of Mayo saw repeated or concurrent activity over a long span of time.