Bangor Cathedral has the oldest Cathedral foundation in Britain on the site of a Celtic Clas and dedicated to St Deiniol in 525 AD. King of Gwynedd named Maelgwn gave the land to Deiniol for establishing a monastery in Bangor. Deiniol became the first Bishop of the newly established Diocese of Bangor in 526 AD.

Pilgrims visit Bangor Cathedral as part of the North Wales Pilgrims Way on their journey to Bardsey Island. When back in the Middle Ages 3 pilgrimages to Bardsey Island were considered equivalent to a pilgrimage to Rome