Innisfallen, one of twenty-four islands scattered across the lake outside Killarney, carries the remains of several distinct religious structures clustered along its northern and north-eastern shoreline, all visible from one another across a remarkably short stretch of ground. Among them are two Romanesque buildings, including a structure known as the Abbot's Church, a small oratory, and what may be a clochán, the dry-stone beehive hut associated with early Irish monasticism. Alongside the standing ruins lie cross-slabs, grave-slabs, a bullaun stone (a boulder with one or more cup-shaped hollows, likely used for grinding or ritual purposes), and a stoup for holy water. The density of remains on such a confined site is quietly arresting.

The island's monastic story is said to begin in the sixth century, when a monastery was reputedly founded here by St Finan, though the earliest surviving structures belong to a much later period. The Augustinian abbey, built by the Canons Regular of St Augustine and dedicated to St Mary, dates to the late twelfth or early thirteenth century, and was constructed on or near the site of that earlier foundation. Innisfallen is also associated with the Annals of Inisfallen, one of the most important chronicles of medieval Irish history, though scholars believe that while later portions of the text were likely transcribed here, earlier sections may have been composed at a larger Munster monastery. After the dissolution of religious houses, the island was granted in 1582 to Sir Richard Collum, and by the end of the sixteenth century had passed to Sir Valentine Browne, Earl of Kenmare. The subsequent earls of Kenmare developed Innisfallen as a tourist attraction during the late seventeenth and early eighteenth centuries, a use that had faded considerably by 1840. In the twentieth century the island came into the ownership of the McShain family, who transferred it along with much of the Muckross Estate to State ownership in 1973. It now forms part of Killarney National Park.

Access to Innisfallen is by boat from Ross Castle on the shores of Lough Leane. The ecclesiastical remains sit along the northern edge of the island, and because several structures are positioned within sight of each other, it is possible to take in much of the complex without covering great distances. The bullaun stone and the smaller fragments reward close attention, as they tend to be overlooked in favour of the more immediately legible abbey ruins.