Clonmacnoise is a spectacular early medieval monastic site set on the banks of the River Shannon in County Offaly, roughly in the centre of Ireland.

Founded in the 6th century, it grew into one of the most important religious and scholarly centres in medieval Europe. The site is accessible by water, making it a notable stop for Shannon cruisers.

The complex includes a cathedral, a well-preserved round tower standing 119 feet tall, three high crosses, and more than 600 carved cross-slabs and memorial stones dating from the 8th to the 12th century.

A 12th-century Norman castle stands near the river's edge. A separate Nuns' Church, a fine example of early Romanesque architecture, lies about 300 metres from the main enclosure. The site is managed by the Office of Public Works and is open year-round.