The two main Saints on Anglesey
King Maelgwn Gwynedd gave Cybi the old Roman fort at Holyhead (subsequently known, in Welsh, as Caer Gybi, "Cybi's Fort") on Holy Island (thence called Ynys Gybi, "Cybi's Island"). He founded a large and important monastery there.
Seiriol was an early 6th-century saint, who created a cell at Penmon Priory on Anglesey, off the coast of North Wales. He later moved to Ynys Seiriol (Puffin Island)
