At Foxhall in County Galway, a subrectangular enclosure, roughly 26 metres from north-east to south-west and 22 metres from north-west to south-east, was recorded on the old Ordnance Survey six-inch maps, the detailed nineteenth-century series that remains one of the most important documents of the Irish landscape. When surveyors visited the site in March 1983, they found flat grassland and nothing else; no earthwork, no ridge, no depression to suggest that anything had ever stood or been bounded there.

And yet the enclosure has not entirely vanished. Aerial imagery captured in 2019 shows its outline still faintly legible from above, a phenomenon known as a cropmark or soilmark, where buried features influence the growth or colour of vegetation above them in ways that only become visible at altitude. Enclosures of this general type in Ireland are often associated with early medieval settlement, a period roughly spanning the fifth to the twelfth centuries, when ringforts and their rectangular equivalents served as enclosed farmsteads. Whether this particular example belongs to that tradition, or to some earlier or later use of the land, is not recorded. What remains is a shape, preserved in the soil beneath an unremarkable field, still just about legible if you know where, and how, to look.