That degree of effort is what makes this earthwork near Donard quietly remarkable. The enclosure itself measures about 33 metres across, but its full extent, once all the outer works are counted, stretches to roughly 60 metres, the whole thing sitting on a west-facing slope where the ground begins to level out into very marshy terrain.

A multivallate enclosure is one defended by multiple banks and ditches, or fosses, and this site deploys them with some complexity. The innermost circuit consists of an earthen bank up to 1.3 metres high with an external fosse running from the north-west around to the south-west, where the ditch gives way to a flat berm rather than continuing. At that south-western edge, where the enclosure meets the marsh, the berm is given a stone revetment, presumably to hold the ground against the wet. Moving outward, a second bank and fosse follow a similar arc, and then a third and fourth bank are separated by a shallow fosse between them; at the south these two banks merge into a single broad, low feature, six metres wide, with a narrow slot or trench cut along its crest. The outermost, fifth bank is also the tallest, reaching 1.6 metres at its highest point, and to the north it is separated from the second bank by an unusually wide berm of around ten metres. Whether the site was a defended settlement, a place of assembly, or something else entirely is not recorded; the careful accommodation of the marshy ground at the south-west, however, suggests that whoever built it understood this landscape well and worked with its peculiarities rather than against them.