Known as Holy Island, or Camillaun Island, it lies in County Mayo, and somewhere near its middle, just north of what was once cultivated ground, a roughly rectangular setting of stones occupies a space about 1.2 metres from north to south and 1.6 metres from east to west. The stones are not touching one another; gaps of between 20 and 50 centimetres separate them, which makes it genuinely uncertain whether this is the remains of a deliberate megalithic construction or something that arrived at its current form through a longer and less intentional history.

The western side of the arrangement is anchored by a large erratic boulder, a stone deposited by glacial movement rather than human effort, which measures nearly 1.84 metres along its north-south axis and stands 1.2 metres high. It has fractured into three pieces along roughly its north-south axis. The northern edge is formed by a substantial stone with a notably flat, vertical inner face, though how deeply it extends below ground is not known. The eastern side involves three stones, two of them set close together and parallel to one another near the northern end, each with flat inner faces, and a third positioned further south. A single, lower stone closes the southern side. The combination of a natural erratic repurposed as one wall and the careful flat-faced positioning of the other stones gives the whole thing an ambiguous quality, hovering somewhere between the geological and the constructed.

The island is now largely given over to scrub and ferns, and the cultivated fields that were worked here until the mid-twentieth century are no longer visible as such, their enclosing walls absorbed back into the vegetation. The stonework sits just to the north of that former cultivation area, on slightly higher ground, which is perhaps why it survived the centuries of farming activity around it.