In the townland of Ballinrooaun in County Galway, a small roughly circular enclosure, approximately twenty metres in diameter, was carefully noted by surveyors in the nineteenth century and then, at some point between that recording and the present day, ceased to exist in any form that the eye can detect. No earthwork, no ridge, no hollow in the ground remains to mark where it stood.

The enclosure appeared on the 1838 edition of the Ordnance Survey six-inch map, the first systematic large-scale mapping of Ireland, which captured hundreds of features, field boundaries, ruins, and earthworks that were already old or fading at the time of survey. Circular enclosures of this kind are generally associated with early medieval settlement, the ringfort tradition that saw farmers and their families enclose their homesteads within a raised bank and external ditch. At twenty metres across, this would have been a modest example, towards the smaller end of the known range. Whether it was levelled deliberately during agricultural improvement, or simply worn down by centuries of ploughing, the map entry is now the only record of its existence.