It is not a building in any conventional sense, more a carefully constructed box, trapezoidal in plan and less than a metre wide at its narrowest end, built from a combination of slate slabs set upright, coursed stonework, and slotted corner stones. Only two of those corner stones survive. It was almost certainly a reliquary shrine, the kind of structure built in early medieval Ireland to house the venerated bones of a saint or significant figure, reinterred after an initial burial and kept in a place of honour within an ecclesiastical enclosure.

Excavation revealed that the shrine was likely extended westward at some point, giving it an original length of roughly 1.1 metres, and that its contents had been disturbed before it was properly investigated. Despite that disturbance, the physical evidence points clearly toward its function as a repository for human bone. The construction technique, particularly the slotted corner stones, connects it to a closely related example on Valentia Island at Cool East, suggesting a regional tradition of shrine-building on the Iveragh Peninsula in which specialist stoneworkers produced recognisable forms across different island and coastal sites. The archaeological survey of South Kerry compiled by A. O'Sullivan and J. Sheehan, published by Cork University Press in 1996, provides the detailed record on which understanding of this structure rests.

Church Island itself sits in Lough Currane, near Waterville, and the shrine is one of several early Christian features on the island. The hollow in which it sits gives it a sheltered, almost secretive quality, easy to overlook among the other stonework unless you know to look for the surviving upright slabs and the slight broadening of the structure toward its western end.