It measures roughly eight metres by six, and rises only half a metre from the ground, which means most people could walk past it without a second thought. That near-invisibility is part of what makes it worth pausing over.

This is a fulacht fia, a type of prehistoric cooking site found in enormous numbers across Ireland, particularly in low-lying or waterlogged ground near water sources. The basic method involved heating stones in a fire until they were intensely hot, then dropping them into a water-filled trough to bring it to the boil. The stones, cracked by repeated thermal shock, were discarded after use, and over centuries of activity they accumulated into the characteristic horseshoe-shaped or oval mounds that survive today. The burnt, fragmented material in these mounds is essentially the spent fuel of a Bronze Age kitchen. The example at Ballynaguilla follows the pattern closely: marshy ground, proximity to a stream, an oval spread of charred and broken stone. It is unexcavated, overgrown, and gives little away on the surface, but the shape and setting are unmistakable to anyone who knows what to look for.