On a rise in rough scrubland at Billymore in County Galway, a ringfort once stood, and the only reliable evidence that it ever did is a marking on a nineteenth-century map. No bank, no ditch, no scatter of stone. The land has reclaimed whatever was there, leaving a site that is, in the most literal sense, invisible.

Ringforts, known also as raths, are among the most common surviving monuments in the Irish landscape, typically consisting of a roughly circular area enclosed by one or more earthen banks and ditches. They date mostly from the early medieval period, roughly the fifth to the twelfth centuries, and are generally thought to have served as defended farmsteads for a single family and their livestock. The Billymore example was recorded on the first edition of the Ordnance Survey six-inch map, which was produced in Ireland during the 1830s and 1840s, making it one of the most systematic early attempts to document the country's topography and antiquities. At the time of that survey, the enclosure measured approximately twenty-five metres in diameter, a modest but not unusual size. By the time the site was catalogued in Paul Gosling's archaeological inventory of west Galway, published in 1993, no visible surface trace survived. Whatever earthworks had remained into the nineteenth century had, in the intervening period, been levelled, eroded, or simply absorbed into the surrounding scrub.