This one, sitting in gently undulating pastureland near Carn in County Galway, came to proper attention only in November 1987, when aerial reconnaissance picked out a poorly preserved enclosure with what looked, from altitude, like the telltale depression of a souterrain, an underground stone-lined passage typically associated with early medieval settlement, used for storage or refuge. It turned out not to be that at all.

When investigators inspected the site on the ground, they found a rath, the most common type of Irish ringfort, essentially a circular enclosure defined by a bank of earth and stone, here measuring roughly 44.7 metres in diameter. The depression that had drawn interest proved to be a quarried-out area in the north-east quadrant, which partly explains the monument's poor state of preservation. More intriguing is what survives inside: a low internal bank, about 1.5 metres wide, running east to west across the enclosed space, dividing the interior in a way that has no obvious parallel in standard rath layouts. Whether this was a later addition, a structural feature of the original design, or something else entirely, the notes do not say. Beyond the enclosure itself, low banks of earth and stone, each around 2 metres wide, radiate outward from the south-west and north-west, and these are interpreted as the possible remnants of an associated field system, suggesting the rath once sat at the centre of a working agricultural landscape rather than in isolation.