On the summit of Croughaun Hill in County Waterford, an ancient cairn has been quietly repurposed by the modern state. Measuring twelve metres across but only half a metre high, the circular mound of large, grass-covered stones is low enough to read almost as a natural feature of the hilltop, until you notice the trigonometric station planted at its centre. That concrete pillar, used by Ordnance Survey teams to fix precise points in the national mapping grid, sits directly atop what is almost certainly a prehistoric funerary monument, the two separated by several thousand years of human interest in high ground.

Cairns of this type, roughly circular accumulations of stone raised over burials or as territorial markers, are a familiar feature of Irish uplands from the Neolithic and Bronze Age periods, broadly spanning from around 4000 to 500 BC. Their builders consistently chose prominent hilltops, a pattern that presumably had as much to do with visibility and landscape significance as with any practical concern. Croughaun Hill fits that logic exactly. The cairn at Kilcanavee is modest in scale compared to the great passage-tomb mounds of the Boyne Valley, but its hilltop position and its construction from gathered field stones follow the same broad tradition. The irony of the trigonometric station is perhaps less surprising than it first appears: surveyors, like prehistoric communities before them, needed the highest and most unobstructed point available, and this particular hill had already been marked out as significant long before the first Ordnance Survey team arrived in Ireland in the nineteenth century.