The Holy Island of Lindisfarne is very atmospheric. It housed a monastery in 635AD, and the site of the castle was built in the 1500s. The Vikings raided Lindisfarne in 793, which was devastating to the island, although a Christian community did survive. The Holy Island is definitely a great place to visit (we went twice; once at 3am), but you have to plan the visit carefully, as the island is cut off twice a day by the tides, and the causeway can’t be crossed (except by boat!).