A rath, as these earthwork enclosures are known, was typically formed by one or more circular banks of earth and sometimes stone, enclosing a farmstead during the early medieval period, roughly between the fifth and twelfth centuries. Thousands survive across Ireland in varying states of preservation. This one is doing its best to return to the landscape.

What remains at Knockacarrigeen is an oval enclosure, measuring approximately 48 metres east to west and 39 metres north to south. The original enclosing bank, now heavily denuded, can still be traced from the southern side around through the west and up to the north. Elsewhere, the boundary has degraded further still, leaving only a scarp, a low sloping edge in the earth, as the sole indicator of where the perimeter once ran. A shallow external fosse, the ditch that would have been dug to throw up the bank material, survives partially on the southern and western sides. Modern field walls have been built directly across the monument at the east, south, and west, cutting through whatever coherence it might otherwise retain. These intrusions are themselves now old enough to seem part of the scene, and together with the eroded earthworks they produce a palimpsest of agriculture across many centuries.