It measures roughly 12.8 metres across and just 0.6 metres high, a subcircular swell in the landscape that most walkers would step over without a second thought. Yet this is the preserved remnant of a burnt mound, a class of prehistoric site found in their thousands across Ireland, typically dating to the Bronze Age, formed through the repeated heating of stones in fire and their subsequent dumping after use in water-based processes.

The accepted explanation for these sites, backed by decades of experiment and excavation, is that the stones were heated in a fire, then dropped into a water-filled trough to bring it rapidly to the boil. The cracked, fire-shattered stones were discarded into a heap nearby, which over time became the mound we see today. What the hot water was actually used for remains a matter of debate, with cooking, bathing, textile processing, and other craft activities all proposed at various points. The Rinrush mound sits in the kind of low-lying, waterlogged ground typical of such sites, close to a small stream that would have provided a reliable water source. Roughly 255 metres to the south-west lies a related site, a fulacht fia, the Irish term commonly applied to the broader category of burnt mound and associated trough complexes, suggesting this part of Rinrush saw repeated or sustained activity at some point in prehistory.