But the shape is too deliberate, and the stream running close to the east side is no coincidence. This is a fulacht fia, one of the most common yet least-understood monument types in the Irish landscape, and its form encodes a very specific prehistoric technology.

Fulachtaí fia are burnt mound sites, found in their thousands across Ireland, and most date from the Bronze Age, broadly between 1800 and 800 BC. The working theory, widely accepted though still debated, is that they functioned as outdoor cooking places. A trough, usually timber-lined or stone-lined and dug into the ground near a water source, would be filled with water. Stones were heated in a nearby fire and then dropped into the trough to bring the water to a boil. The cracked and shattered stones were then discarded to the sides, and over generations of repeated use they accumulated into the characteristic horseshoe or kidney shape that survives today. The mound at Moyny measures roughly ten metres north to south and eight metres east to west, standing about 0.6 metres high, with an opening facing east-south-east at around 1.8 metres wide. That opening is where the trough would have sat, orientated towards the stream that still flows to the east, the same water source the Bronze Age users would have relied upon. The persistence of that stream beside a monument several thousand years old is one of those quietly unsettling continuities the Irish countryside occasionally offers.