A monastery founded by St Kentigern, also known as Mungo, has existed nearby since the late 6th century. Kentigern left the mobastery in the care of Asaph after whom the locality has been known ever since. The current cathedral is the smallest in Wales and dates from 1285, a reconstruction after the destruction of its predecessor by the troops of Edward I in his wars against Llywelyn ap Gruffydd for control of Gwynedd.