At Ardagh in County Galway, a ringfort once occupied a modest circle of ground in gently undulating pastureland, and the only surviving evidence of its existence is a line on a nineteenth-century map. A ringfort, to give the briefest context, is a roughly circular enclosure defined by an earthen bank and ditch, and was typically used as a farmstead during the early medieval period. Thousands of them were built across Ireland, and thousands have since been ploughed out, built over, or simply worn away by centuries of agricultural use. This one, measuring approximately twenty metres in diameter, has left no visible surface trace at all.

What we know comes from the first edition of the Ordnance Survey six-inch map, the great mid-nineteenth-century cartographic project that systematically recorded Ireland's landscape at a time when many ancient features were still legible on the ground. When surveyors passed through Ardagh, they recorded a circular enclosure here. At some point between that survey and the present day, whatever remained of the bank or ditch was lost entirely. By the time the site was catalogued for the Archaeological Inventory of County Galway, compiled by Olive Alcock, Kathy de hÓra, and Paul Gosling and published in 1999, there was nothing left to describe beyond that early map marking and the general character of the surrounding land.