There is something quietly unsettling about a monument that has effectively vanished from the surface of the earth while remaining, technically, present. At Knockhouse in County Waterford, a circular embanked enclosure sits in ordinary pasture on a gentle south-facing slope, and yet a visitor standing on the ground above it would see nothing at all. The earthwork has been absorbed so completely into the surrounding landscape that it is invisible at ground level.

The enclosure was still legible enough in 1840 to be recorded on the first edition of the Ordnance Survey six-inch map, where it appeared as a roughly circular form with an external diameter of somewhere between 35 and 40 metres. By the time the 1926 edition of the same map was produced, the picture had already changed considerably. What had once read as a complete circuit was by then reduced to a fragment of bank measuring approximately 25 metres east to west and 15 metres north to south, with the eastern and southern portions cut away and the northern and western edges truncated by field boundaries. In other words, the slow ordinary business of farming, the laying out of field banks and the management of grazing land, had been steadily eating into the monument across the intervening decades. Embanked enclosures of this kind are broadly associated with early medieval settlement in Ireland, though without excavation the precise date and function of any individual example can rarely be established with confidence.