The town itself began in 1295 when Edward I of England started to build Beaumaris Castle . This was one of several castle along the North Wales coast - others include Conwy , Caernarfon and Harlech . Beaumaris was originally a Viking settlement known as Porth y Wygyr ( `` Port of the Vikings '' ) , but the town itself began its development in 1295 when Edward I of England , having conquered Wales , commissioned the building of Beaumaris Castle as part of a chain of fortifications around the North Wales coast ( others include Conwy , Caernarfon and Harlech ) .