A circular enclosure roughly eighteen metres in diameter once occupied a patch of level, marshy grassland here, and the only reliable record of it is a line drawn by Ordnance Survey cartographers in 1838. Today, no visible trace of it survives at the surface. The ground holds no obvious earthwork, no raised rim, nothing to catch the eye of a passing walker. What remains is essentially a ghost of a boundary, documented once and since swallowed by the wet ground.

The 1838 Ordnance Survey six-inch map, the first systematic large-scale mapping of Ireland, recorded the enclosure as a clearly circular form. Enclosures of this kind are common across the Irish landscape and most are thought to be early medieval in origin, functioning as farmsteads or settlement enclosures, though without excavation it is rarely possible to say more with certainty. What makes the Derrydonnell Beg example quietly notable is both its near-total disappearance and its proximity to a second enclosure, recorded as lying only about twenty-five metres to the south-east. Two such features sitting so close together suggests this corner of south Galway may once have held a small cluster of activity, the details of which the marshy ground has since absorbed entirely.