At Lackenduff in County Cork, a ringfort sits atop a low hillock on a north-north-west-facing slope, recorded, classified, given a grid reference, and yet entirely invisible to anyone standing in the field above it. No earthwork, no bank, no ditch. Just pasture.

A ringfort, or rath, is the most common type of early medieval monument in Ireland, typically a circular enclosure defined by one or more earthen banks and ditches, enclosing a farmstead or high-status residence dating roughly from the period between 500 and 1000 AD. Thousands survive across the country in varying states of preservation. This one at Lackenduff was recorded as a semicircular arc of enclosure on the Ordnance Survey six-inch map of 1842, meaning it was at least partially legible to surveyors in the nineteenth century. The southern portion had already been truncated by a field fence at that point, suggesting the monument was being slowly absorbed into the working agricultural landscape even then. At some stage after 1842, whatever remained above ground was levelled entirely, leaving no visible surface trace.