Founded in Ardfert by St. Brendan 'The Navigator' in the 6th century, there are three medieval churches, two ogham stones and a number of early Christian and medieval grave slabs on the site today. The earliest building is the cathedral which dates from the 12th to 19th centuries. It has a fine Romanesque west doorway, a magnificent 13th-century east window and a spectacular row of nine lancets in the south wall. Two effigies of ecclesiastical figures of late 13th to early 14th-century date which were mounted on either side of the east window are on view in the South Transept. The battlements were added in the 15th century. The pre-12th-century block of masonry is clearly visible on the north wall.