Somewhere in the gently rolling pastureland of east Galway, overlooking a stretch of marshland to the north-west, a ringfort once stood that has since been reduced to little more than a faint crease in the ground. A ringfort, or rath, is a roughly circular enclosure defined by an earthen bank and ditch, built during the early medieval period as a farmstead and enclosure for livestock. They survive in their thousands across Ireland, but this one did not.

The Ordnance Survey six-inch maps recorded it as a roughly circular enclosure approximately 45 metres in diameter. When archaeologists inspected the site in April 1984, the outline was barely discernible above ground level. Local knowledge filled in the gap: the feature had been a fort, people said, and it had been levelled around 1979 during land-improvement works. That single phrase, land-improvement works, covers a great deal of twentieth-century Irish agricultural history, a period when field drainage schemes and the clearing of inconvenient earthworks erased a considerable portion of the country's early medieval landscape. The monument at Lisduff was one such casualty, gone within living memory by the time anyone came to record it formally.

What remains is visible not on the ground but from above. Aerial photographs show the outline of the enclosure clearly enough, the subtle difference in soil moisture and crop growth that betrays the presence of a filled-in ditch long after the bank has been ploughed flat. It is a reminder that even erased monuments leave traces, just not the kind you can walk around.