This is the Claí Rua, the Red Ditch, or as locals have long called it phonetically, the Cleeroo. It appears on Ordnance Survey maps from 1840 to 1841 and again in 1916 as the "Track of Red Ditch", and its possible starting point lies just north of Cahercarbery (More) promontory fort on the Kerry coast. What it actually is, a territorial boundary, a drove road, a political frontier, nobody has fully settled.

The earthwork was first noted in print by Smith in 1756, who traced it running up Triskmore Mountain before it drops out of sight for roughly 3,700 metres and reappears on the east summit of Maulin Mountain. Smith also described it crossing the Cashen river, continuing over Knockanure Mountain and pushing on into County Limerick, a claim repeated by Westropp in 1909, who further recorded it forming the southern boundary of Glenlea and continuing by an old path through Booleenshare. Beyond that point, a notable clustering of ringforts, the enclosed farmsteads that characterise early medieval Ireland, appears along its route, which has prompted the suggestion that the ditch may have actively shaped settlement in the area, perhaps acting as a frontier that drew people to its edge. Both Smith and Westropp believed the Claí Rua may connect ultimately with the Claí Dubh na Rátha near Charleville in County Cork. O'Conchuir, writing in 1987, proposed that the earthwork might mark the limit of an Uí Bhriain territorial advance against the Ciarraighe, a local dynasty of Kerry. The comparison that gives the idea real weight is with the Black Pig's Dyke, the long linear earthwork in Ulster that once defined the ancient boundary of the Ulaidh; the Claí Rua belongs to the same tradition of large-scale landscape division, even if its precise origins remain unresolved. What local oral memory preserved was something more mundane but equally vivid: the ditch served as a road, used by ordinary people carrying goods to markets across the Limerick border.

What survives today is modest in scale. The bank to the south-west measures 1.7 metres wide and just 0.4 metres high; the ditch beside it, originally flat-bottomed, is 0.7 metres wide and drops only 0.3 metres below the surrounding ground. You would walk over it without knowing, unless you were looking.