At Ballynamrossagh, though, the curve is too deliberate, the proportions too consistent to be accidental. What survives here is a rath, the Irish term for a ringfort, the type of enclosed farmstead that once defined the rural landscape of early medieval Ireland, roughly between the fifth and twelfth centuries. Thousands were built across the country, each one a statement of modest domestic authority, a family's claim on a patch of workable land.

The Ballynamrossagh example is a circular enclosure roughly twenty-six metres in diameter, sitting on a north-north-westward-facing slope. Its boundary is formed by a combination of features: a scarp, essentially a cut into the hillside that creates a stepped edge, running around the southern and northern arc; a low earthen bank along the southern and south-western side; and an external fosse, a shallow ditch, tracing the eastern and north-western perimeter. The bank reaches about forty centimetres above the interior ground level, while the ditch runs to between twenty and thirty centimetres in depth. These are modest dimensions, suggesting a site that was never heavily defended but simply delineated, a working enclosure rather than a fortress. A probable entrance, around four metres wide, opens at the north-north-west. Inside, the ground slopes gently in the same north-north-westward direction, and the enclosure is dotted with occasional deciduous trees, with a tangle of briars filling the south-east quadrant.