Raths, the earthen enclosures that once served as defended farmsteads across early Christian Ireland, are common enough on the mainland. Finding one this well-preserved on a tidal island is rather less ordinary.

The fort occupies the eastern end of Inishkeel Island, straddling the spine of a narrow ridge that runs the length of the island east to west. This elevated position would have given its inhabitants clear sightlines to the mainland, roughly 200 metres to the northwest, and to the scatter of islands lying to the north and east. The structure itself is a raised circular enclosure, about 24.5 metres across internally, defined by an earthen bank and surrounded by an external fosse, the term for the defensive ditch dug around such an enclosure. The bank is particularly substantial and well-preserved along its northern arc, standing some 3.3 metres high on the exterior. To the south it is lower and less distinct, though the outer scarp remains pronounced. The fosse, around 3.5 metres wide, is clearly legible on the northern side as a flat-bottomed depression, while to the south it becomes a waterlogged shelf. A slight outer rise at the south-southwest may be what remains of an additional external bank, adding another layer to what was already a carefully constructed defensive arrangement. The entrance is a ramp-like gap, two metres wide, on the eastern side, with a broad causeway across the fosse that may have been widened at some point in more recent centuries. Oral tradition holds that the interior conceals a souterrain, an underground stone-lined passage of the kind used in early medieval Ireland for storage or refuge, though two low sod-covered mounds in the northern interior are more likely the result of field clearance.

Access depends entirely on the tide. The island sits around 200 metres from the mainland shore, and the crossing on foot is only possible at low water. The rath sits on the ridge at the eastern end, in open pasture, and the elevation means it is visible from some distance once you are on the island.