The enclosure at Derryronan is easy to miss: the bank that defines it rises barely thirty centimetres above the interior ground level, and in places dips even lower than the land outside. Two later field walls cut straight across the interior, and a third stretch of the original stone bank has been repurposed as part of a more recent boundary. The place has been worked over, divided, and partly forgotten, yet the rough circle, measuring roughly twenty-seven metres east to west and just over twenty-five metres north to south, is still legible in the landscape if you know what to look for.

By 1838, when the Ordnance Survey produced its first detailed six-inch map of Ireland, this feature was already being recorded as a circular embanked enclosure, the kind of ring-bank associated broadly with early medieval settlement. By the 1930 revision, cartographers were representing it instead as a polygonal shape folded into the local field pattern, reflecting how thoroughly the original form had been reworked. A rath, which is an earthen ringfort typically associated with early Irish farming families, lies about a hundred metres to the north, while a cashel, the stone equivalent of a rath, sits roughly two hundred and thirty metres to the north-east. A possible crannog, an artificial or partially artificial island used as a lake dwelling, has been identified about two hundred and forty metres to the west. The concentration of these different enclosure types in such close proximity suggests this corner of Mayo was once a fairly densely settled or at least repeatedly occupied stretch of ground. Local tradition also holds that a cross-inscribed stone is associated with a nearby enclosure, hinting at an early Christian presence in the area, though its current condition and precise location are not fully documented.