The earthwork at Doon Hill is a rath, the term used for a ringfort, the enclosed homestead type that was the dominant form of rural settlement in early medieval Ireland. This particular example is roughly oval in plan, measuring approximately 45 metres on its longer northeast to southwest axis and around 20 metres across. What sets it apart is not its scale but its internal detail: two banks with a fosse, or ditch, between them define the enclosure, and within the interior, which sits slightly above the surrounding ground level, parallel lines of set stones run between gaps on the eastern and west-northwest sides. These stone lines may preserve the trace of an original trackway passing through the site, a rare and quietly suggestive survival.

The causewayed gaps in the banks on opposite sides of the enclosure may themselves be original entrances rather than later breaks, which would mean the trackway was a deliberate feature of the design, built to allow passage through rather than simply into the enclosed space. In the southwest quadrant, an L-shaped hollow hints at something else beneath the surface: a probable collapsed souterrain, an underground stone-lined passage or chamber typically used for storage or concealment. The site was noted by H. T. Knox, whose work on Galway antiquities appeared in 1918, and the rath remains in fair condition, a reasonable state of preservation for an earthwork that has been sitting in agricultural land for well over a thousand years.