There is something quietly unsettling about an archaeological feature that exists in the historical record but refuses to show itself on the ground. At Duagh in County Waterford, a small embanked enclosure, roughly thirty metres in external diameter, sits in pasture at the base of a south-facing slope where the land gives way to marsh. Walk across the field and you would see nothing out of the ordinary; the enclosure is simply not visible at ground level.

What we know of it comes from the 1840 edition of the Ordnance Survey six-inch map, one of the most ambitious cartographic undertakings in nineteenth-century Ireland, which recorded landscape features with a precision that has since allowed archaeologists to identify sites that later land use has effectively swallowed. An embanked enclosure of this kind, a roughly circular area defined by a raised earthen bank, is a common enough monument type in the Irish countryside, associated variously with settlement, ritual, or agricultural use depending on period and context. Here, though, the combination of its low-lying position at a marsh edge and its total invisibility at surface level makes it a peculiar case. Whether the bank has been levelled by ploughing or simply subsided into the soft ground over time is not recorded.