In the pastureland around Ballinlug in County Westmeath, a ringfort, the circular earthwork enclosure that served as a farmstead and defended homestead for much of early medieval Ireland, once occupied a stretch of fairly level ground, with the land climbing away to the east and south-east. Today there is nothing to see. No bank, no ditch, no ridge in the grass to suggest that anything was ever there at all.

The paper trail, however, is surprisingly persistent. An estate map drawn in 1776, now held in the National Library of Ireland, marks the site as a circular enclosure rendered in a double dotted circle, a cartographic convention suggesting the surveyor recognised it as a ringfort or something very like one. The same feature reappears on the 1837 Ordnance Survey Fair Plan map, drawn with similar intent. By the time the more familiar 1837 OS six-inch map was produced, the enclosure had already begun to lose definition; it appears only partially, as a curving field boundary to the west of a farm building, the archaeology gradually absorbed into the working landscape around it. A field inspection carried out in 1983 confirmed what those maps had quietly implied: no surface remains were visible. Aerial photography has since found nothing either.

What the Ballinlug site illustrates is how thoroughly a monument can be erased while its outline continues to echo through successive layers of record. The ringfort almost certainly vanished through gradual agricultural clearance, the banks levelled and the ditches filled over generations of ploughing and drainage. The 1776 estate map becomes, in retrospect, something close to the last reliable witness.