Two fields west of where Tarmon Castle once stood in north County Kerry, Ordnance Survey mapmakers recorded a circular enclosure in the 1840s, and again in 1914, and today there is nothing there at all. No earthwork, no ring of stones, no slight rise in the ground. Whatever the surveyors saw, or understood themselves to be recording, has since vanished entirely from the landscape.

Circular enclosures of this kind are common enough across Ireland to have their own shorthand in archaeological literature. They are frequently the remains of ring forts, known in Irish as raths or liosanna, which were the enclosed farmsteads of early medieval Ireland, typically defined by one or more earthen banks and ditches. Some are ecclesiastical in origin, marking out the boundaries of early monastic or church land. The townland name Tarmon is itself suggestive on this point: it derives from the Irish tearmann, meaning sanctuary or church land, a term that usually indicates early Christian association with a particular territory. Whether this enclosure was domestic, ecclesiastical, or something else entirely is impossible to say now. What can be said is that it was considered significant enough to map twice across seventy years, and that its disappearance since then, most likely through agricultural levelling, has left the ground with no visible trace of what once defined it.