Somewhere in the process of building a road, a piece of prehistory quietly lost its eastern edge. At the bottom of the Nier river valley in County Waterford, a low grass-covered platform sits on a knoll above a south-west-facing slope, the remnant of what was once a circular embanked enclosure roughly thirty metres across. The road that now cuts through it appears on the Ordnance Survey six-inch map of 1840, meaning the damage was already done by the time anyone thought to record the site formally. What remains has been pressed into a D-shape, defined by a slight scarp on three sides, the eastern arc simply gone.

Circular embanked enclosures of this kind are a recurring feature of the Irish landscape, typically interpreted as enclosed farmsteads or settlement sites, broadly prehistoric or early medieval in origin, though without excavation it is rarely possible to be more precise. They are sometimes called ring forts or raths, earthwork enclosures in which a bank and internal ditch surrounded a domestic space. The example at Clonanav measures roughly thirty metres from north-north-west to south-south-east, and about seventeen metres across its shorter axis, dimensions that fall within the typical range for a single-family enclosure. Its position on a knoll above the valley floor is also characteristic; such sites were regularly placed on slightly elevated ground, giving a degree of visibility and drainage without sacrificing access to the river and the agricultural land below.

The surviving scarp is slight enough that the platform could easily be overlooked, particularly where the truncated eastern side blends into the road margin. What a careful eye will find, though, is a distinct flattening of the knoll's summit, the faint geometry of something deliberately made.