It is, in fact, a rath, the Irish term for a ringfort, the kind of enclosed farmstead that tens of thousands of early medieval families built across Ireland, typically between the sixth and tenth centuries. This one at Carrowduff measures roughly 23 by 24 metres, nearly circular, and is encircled by a flat-bottomed fosse, a shallow ditch that would originally have helped define the boundary between the domestic world inside and the wider landscape without.

The site sits on poorly drained ground, with higher land rising to the east and south, which means the interior slopes gently downhill toward the north. The enclosing earthen bank survives in varying condition around the circuit: best preserved from the southeast to the northwest, where its outer face still stands between 0.8 and 1.3 metres high, though it has been worn down to a simple scarp at the northeast and partially robbed out on the western side, the bank material likely taken at some point for use elsewhere on the farm. A gap on the southern side is considered modern, probably a later agricultural convenience, while a narrow causeway at the north-northeast, about 1.4 metres wide, may represent the original entrance across the fosse. The rath was already being mapped in the nineteenth century, appearing on both the 1840 and 1916 Ordnance Survey six-inch sheets, which suggests it was a legible feature in the landscape even then, if not always understood for what it was.

The interior today is featureless and clear of excess vegetation, with a field drain running along the northern perimeter. Nothing visible on the surface points to what daily life inside once looked like, though such enclosures typically contained timber or wattle structures, animal pens, and storage pits, all long since dissolved back into the ground.