In Castletown, County Kerry, a ringfort once occupied enough space and prominence to be recorded as a circular enclosure on the Ordnance Survey maps of 1841 to 1842, and again on the revised maps of 1898. Today, no visible trace of it remains.

Ringforts, known in Irish as ráth when defined by an earthen bank and ditch, were among the most common settlement forms in early medieval Ireland, typically dating from roughly the fifth to the twelfth centuries. They served as enclosed farmsteads, the bank and ditch providing a boundary as much social as defensive. The fact that this one in Castletown appeared on two separate OS surveys, decades apart, suggests it was still discernible as a feature in the landscape well into the late nineteenth century. What happened between 1898 and the present day is unrecorded, but the causes are familiar enough: agricultural improvement, land clearance, the deep ploughing that accompanied changing farming practices. The earthworks that once defined the enclosure have been levelled entirely, leaving only the cartographic ghost of two map editions to confirm it ever stood.