Lying 2km offshore from Mountshannon, Holy Island (Inis Cealtra) is the site of a monastic settlement thought to have been founded by St CáimÃn in the 7th century. Operators who will take you over to the island include local historian Gerard Madden, who runs two-hour tours from Mountshannon's pier.
The island has a round tower over 27m tall, along with the ruins of several churches, a hermit's cell and some early Christian gravestones dating from the 8th to 12th centuries.
One of the chapels possesses an elegant Romanesque arch and, inside, an old Irish inscription that translates as 'Pray for Tornog, who made this cross'.
The Vikings treated this monastery roughly in the 9th century, but it flourished under the protection of Brian Ború and others. During the 17th century as many as 15,000 people would make Easter pilgrimages here.
