Geologically, the Duvillaun islands do not belong to the Mullet. The Mullet Peninsula is built largely of schist, slate, gneiss, and white psammite, with a granite outcrop at Termon Hill. The Duvillauns are quartzite - the same hard, white, ancient rock that forms the spine of Achill Island twenty kilometres to the south. This is why they survive as islands at all: the quartzite is more resistant to the Atlantic's grinding than the softer surrounding seabed. While the nearby Inishkeas and Inishglora are crowned with brilliant white sand and shell-rich machair grassland, the Duvillauns wear blanket bog - the same slow-growing, water-saturated peat habitat found across the western Irish mainland.

Since the last human residents departed, the Duvillauns have become one of the more important seabird colonies on this stretch of coast. Fulmars and kittiwakes nest on the cliffs in white-streaked rows. Peregrine falcons hover above them, watching for any chick or smaller bird that strays too far. Storm petrels and Leach's petrels - secretive, mostly nocturnal seabirds the size of a swallow - shelter among the abandoned cottages and stone walls of the old settlement, slipping out at dusk to feed across the open ocean. Shags, cormorants, choughs and terns are also present. The Duvillauns are now protected as a bird sanctuary, free from the dogs, cats, and rats that follow human habitation.

Walk inland from the eastern shore of Duvillaun More and you come to one of the most remarkable Early Christian sites on the entire western seaboard. There are monastic remains here dating from the sixth to eighth centuries AD - the same period as similar sites on Inishkea South and Inishglora. The most striking feature is a Gallarus-type oratory - a small dry-stone chapel similar to the famous Gallarus Oratory in County Kerry. Beside it stands a stone tomb formed by large slabs, one of which is six feet two inches tall and inscribed on its western side with a depiction of the crucifixion. The carving is weathered but still clear. Local tradition calls the structure 'Uaimh na Naoimh' - 'the Saint's Tomb' - though, unlike the nearby Inishglora, no specific saint is associated with the island. Beehive huts of similar age stand nearby, their corbelled stones still holding their shape after thirteen centuries on this exposed Atlantic edge.

There is no scheduled passenger service to the Duvillauns. In summer, boat trips leave from Blacksod Pier on the Mullet Peninsula and from Aughleam, taking visitors out to the various offshore islands depending on weather and tide. The crossing to Duvillaun More from Falmore at the southern tip of the Mullet is only about a kilometre, but the Atlantic in this corner is unpredictable; landings often require a calm day and a small dinghy launched from the main boat. Once ashore, you can walk freely. Mind the nesting birds. Stand at the Saint's Tomb and look back toward the Mullet, then west toward the open ocean. The early Christian monks who carved this crucifixion chose this place deliberately - far enough from the mainland to feel like a true retreat, close enough to maintain occasional contact, exposed enough that the prayers might carry.