Somewhere in the rolling pastureland of Rathmuck in County Kildare, half a ringfort survives. That is not a figure of speech. What remains of this early medieval enclosure is, by best reckoning, the western half of what was once a circular earthwork, the eastern portion having been lost entirely to the centuries. What the first edition Ordnance Survey map recorded in 1838 appears as a C-shape, open to the east, with an estimated maximum extent of around 45 metres north to south.

Ringforts, or raths, were the most common form of rural settlement in early medieval Ireland, typically consisting of a circular area enclosed by one or more earthen banks and ditches, used as a farmstead or place of refuge. This one at Rathmuck is now barely legible in the landscape. The surviving arc of the perimeter has been entirely overgrown and is only detectable as a low scarp, no more than 0.4 metres in height, running from the south-west around through the west to the north. The bank that once defined it has long since settled and spread into the surrounding ground. Whatever stood inside, and whatever lay to the east, is gone without record.