Officially it is catalogued as a cashel, a type of ringfort defined by a drystone wall rather than an earthen bank, but locally it is called Oileán an Bhalla, meaning roughly "the island of the wall". That second name hints at something the formal description only implies: at certain water levels, this modest oval enclosure sits close enough to the lough's edge to feel thoroughly cut off from the surrounding land.

The cashel measures roughly 18.7 metres on its north-west to south-east axis and 12.8 metres across, making it a compact structure even by the standards of early medieval stone enclosures. Its drystone wall, built without mortar in the tradition of so many Connemara field boundaries and ancient monuments alike, originally stood to around three metres in height and between one and a half and nearly three metres thick. Much of it has collapsed over the centuries, though the stretch running from the east around to the south-south-west remains the best preserved section. What draws the eye almost as much as the wall itself is a small quay on the northern side, noted by the traveller and archaeologist Henry Layard as far back as 1897 and mentioned again in Lord Killanin's 1954 survey of the area. The quay suggests that access to this place was, at some point, primarily by water, lending the site a character that is more lacustrine outpost than conventional farmstead enclosure.