This one, sitting on a gentle rise in improved pasture near Rockfield in County Mayo, escaped the Ordnance Survey entirely. It does not appear on the OS six-inch maps at all, and its existence only came to light in 1993 when Gerry Walsh identified it from aerial photography. That a site of this kind could remain off the official record well into the late twentieth century says something about how easy it is to overlook earthworks that have been quietly levelled and grazed over for generations.

A rath is an early medieval farmstead enclosure, typically defined by one or more earthen banks and ditches, and this example fits that description in outline if not in crisp preservation. The remains form a roughly circular area, approximately 32 metres north to south and 33.5 metres east to west. On the north-northwest to northeast arc, where the ground naturally falls away, a more substantial earthen scarp survives to around 1.5 metres in height, built up deliberately to maintain a level interior platform. Elsewhere, the enclosing element has been reduced to a faint undulation in the ground. A few large stones protrude from the scarp on the northern side. Just outside that northern arc there is a narrow terrace, roughly two metres wide, which may be the surviving trace of a fosse, the external ditch that would originally have accompanied the bank. Inside the enclosure, near the centre, a slight circular rise of five to six metres in diameter is still discernible, with a shallow dip in the ground immediately to its north. What that interior feature represents is unclear, but it is the kind of anomaly that tends to reward closer attention.

The site sits only a few metres east of the N17, which runs along the western edge of the field. The prominent rise on which it stands commands good views to the north and east, which is precisely the kind of position early farming communities tended to favour when choosing where to build. The southern aspect is more closed, rolling away into undulating terrain.