The island is trapezoidal in plan, about sixty metres along its longer axis and thirty metres wide, and is known locally by the rather blunt name Oileán an Chaca. The enclosing wall, now poorly preserved, survives to around one and a half metres in height and between one and a half and nearly two metres in width, enough to give a sense of the original structure even in its diminished state.

In the south-west corner of the enclosure sits a subcircular structure roughly six metres across internally, tentatively identified as a hut, which would have provided shelter for whoever occupied or used the island. More telling, perhaps, are the features at the margins: the remains of a small quay at the north-north-west corner, and traces of a natural causeway running westward from the island. These suggest deliberate, repeated use of the site rather than occasional refuge, with the quay indicating that boats were part of daily life here. The site was noted by Layard in 1897 and by Tim Robinson, the cartographer and writer who mapped Connemara in meticulous detail, in 1985. Cashels of this kind are associated broadly with the early medieval period in Ireland, when island and lakeshore sites offered both practical advantages, in terms of defence and fishing, and a degree of natural separation from the surrounding landscape.