Clonmacnois (in County Offaly, Ireland) is known as one of the oldest (if not the oldest of all) Christian churches in Ireland, founded in the year AD 547. At the same time, Clonmacnois is thought to be one of the original sources of the Celtic high cross. In Clonmacnois, I had the opportunity to examine more than 1400 years of mortuary art related to the Celtic cross motif.