On a mountain in County Waterford, a single stone rises from the ground at the head of the Colligan river valley, unremarked and largely unvisited. It is not particularly tall, standing just 1.2 metres high, and its triangular cross-section gives it an angular, almost accidental quality, as though it might be a natural outcrop rather than something deliberately set upright. But standing stones of this kind, erected during prehistory across Ireland and Britain, were almost certainly placed with intention, even if that intention is now entirely beyond recovery.

The stone sits in a north-south valley carved out by the headwaters of the Colligan river, with the river running roughly seventy metres to its east. It is made of conglomerate, a rock composed of rounded fragments of older stone bound together in a sedimentary matrix, which gives its surface a rough, pebbly texture quite different from the smooth-faced granite or sandstone more commonly associated with prehistoric monuments. Its dimensions are modest: 1.2 metres along its north-south axis, 0.5 metres east to west, and 1.2 metres in height. Whether it marked a boundary, a burial, a routeway, or something else entirely, no surviving evidence says.