On the eastern slope of a ridge at Kilmannin in County Mayo, what was once formally catalogued as a prehistoric enclosure turns out, on closer inspection, to be almost certainly nothing of the sort. The circular feature that prompted the classification is, in all likelihood, a disused sandpit worked into the slope, and the enclosure, if it ever existed, has long since been obliterated by quarrying. It is, in short, a scheduled monument that may never have been a monument at all.

The confusion is understandable given how the site appears across successive map editions. The 1838 Ordnance Survey six-inch map records nothing at this location. By the time the twenty-five inch plan was produced, an oblong quarried area, roughly 33 metres north to south and 25 metres east to west, appears outlined by hachuring, the fine radiating lines cartographers used to suggest sloping or disturbed ground, accompanied by a limekiln and buildings to the east. The 1916 six-inch edition shows a similar hachured area. Taken together, those maps trace the working life of an industrial extraction site rather than the outline of a prehistoric settlement. Today, the eastern edge of the pit is bordered by the ruins of a house, and the ridge immediately to the west is covered by a dense growth of gorse that makes any further investigation of the ground beneath it effectively impossible. The sandpit, the ruined house, and the impenetrable scrub together form a quietly awkward assembly, a place where the paper record and the physical reality have drifted apart over the course of more than a century.