At Lissaniska in County Mayo, a circular enclosure once stood in undulating pasture, recorded on the Ordnance Survey map of 1838 and likely ancient in origin. Today it has been entirely levelled, leaving no surface traces whatsoever. What you would stand on, if you went looking, is ordinary farmland with nothing to show for what once marked this spot.

The enclosure is tentatively identified as a ringfort, the most common type of early medieval settlement monument in Ireland. Ringforts, typically circular areas enclosed by an earthen bank and ditch, served as farmsteads for rural families roughly between the sixth and twelfth centuries, though some examples are older. Thousands were built across the island, and a significant proportion have been lost to agriculture over the centuries, their earthworks gradually worn down by ploughing and grazing until nothing remains above ground. The Lissaniska example had already been noted on the first Ordnance Survey mapping in 1838, which means it was at least partially visible at that point, but at some time between then and now it was levelled completely. Whether it was a modest single-banked enclosure or something more substantial is no longer possible to say from surface evidence alone.