That kink is not a cartographer's error. It marks the point where a much older earthen arc was absorbed into a working field wall, its original purpose long since obscured by the practical logic of agricultural enclosure. The feature still survives in pasture on undulating ground that falls away to the west towards a stream, and it retains enough physical presence to prompt questions. The arc of bank, oriented roughly south-southwest to north-northwest, runs somewhere between fifteen and twenty metres along its north-south axis, stands up to two metres high on its western side, and measures around three and a half metres in width. That it has survived at all is partly due to the density of blackthorn that has grown up around it, effectively armour-plating the earthwork against casual disturbance.

Local tradition holds that this was once a fort, or possibly a burial place, and neither reading is implausible given the wider landscape. A rath sits roughly a hundred metres to the south; a rath being a roughly circular earthen enclosure, typically of early medieval date, used as a defended farmstead. Whether the arc at Rathrowan represents the remnant of a similar enclosure, something older, or something else entirely is not recorded. What survives on the surface gives only partial clues: an irregular scatter of field clearance stones projects eastward from the southern end of the bank, accompanied by two smaller stone heaps and a shallow stony hollow nearby. These could be incidental accumulations from centuries of farming, or they could hint at something that once stood here before the stones were pushed aside and the bank was quietly pressed into service as a boundary.