Merlin’s cave, under the Tintagel Castle which is situated on the rugged north coast of Cornwall. Legend has it that Merlin was the teacher of King Arthur. Excavations have revealed ruins dating to the 5th century AD when, after a period as a Roman settlement and military outpost it is thought to have been the stronghold of a Celtic king. The medieval castle that can still be seen was built by the Earl of Cornwall between 1233 and 1236.