The enclosure at Knockereen in County Galway belongs to that category. It survives now only in ink and paper, a circular feature that was mapped twice over the course of several decades and found to be diminishing on each occasion, before vanishing from the ground altogether.

The first Ordnance Survey six-inch map recorded a circular enclosure roughly forty metres in diameter at Knockereen, set in level grassland. By the time the third edition of the same map was produced in 1920, something had changed. The feature shown was considerably smaller, around twenty metres across, and appeared to be filled with gravel, suggesting either deliberate clearance or gradual agricultural encroachment in the intervening years. Enclosures of this type are generally understood as the remains of enclosed farmsteads or settlements, most commonly associated with the early medieval period in Ireland, though without excavation the date and function of any individual example remains uncertain. Local information gathered at some point before the site was formally catalogued indicated that the surrounding area had been reclaimed approximately fifty years prior to that record being compiled, a process that would have erased whatever earthworks or surface traces remained. Nothing is now visible on the ground.