These are leachts, a form of commemorative or devotional cairn associated with early Irish Christianity, and as recently as the nineteenth century people were still walking circuits around them in a practice of ritual prayer known as "rounds". That the tradition persisted so long, on an island that requires a deliberate effort to reach, says something about how seriously this place was regarded.

Illauntannig is the largest of the Magharee Islands, a small archipelago lying off the northern tip of the peninsula between Brandon Bay and Tralee Bay in County Kerry. The island contains one of the more complete early Christian monastic settlements known from the west of Ireland. Protected by a substantial cashel wall, a dry-stone enclosure of the kind commonly used to define sacred or defended space, the site holds two small oratories, three beehive huts (corbelled stone cells of a type used by early monks as individual dwelling spaces), a souterrain, a burial ground, a stone cross, three cross-slabs, a bullaun stone (a rounded depression in rock used for grinding or ritual purposes), and fragments of five quern-stones. A hand-bell was also found within the enclosure, and a second bullaun stone sits near the sea about a hundred metres to the south. The three leachts themselves are oriented roughly north-northeast to south-southwest and range between roughly four and five metres in length, standing about a metre high.

The island is accessible by boat from the mainland near Fahamore, and the crossing, while short, depends on weather and sea conditions. Once ashore, the cashel enclosure is the dominant feature, and the leachts are found within it. The quartz pebbles covering their surfaces are worth noting; quartz had long-standing ritual associations in Irish tradition and their presence here is unlikely to be accidental.