Tintagel Castle

http://www.kingarthursknights.com/structures/tintagel.asp 

Tintagel - Cornwall, England
Perhaps the most familiar of all the sites associated with Arthur. Local tradition, founded largely on the writings of Geoffrey of Monmouth in his twelfth-century History of the Kings of Britain, claims this is the birthplace of Arthur, from 

The first gate into Tintagel Castle.

where Merlin took him to be fostered in secret. The dramatic ruins of the castle, dating from the twelfth or thirteenth centuries, are too late to have anything to do with the real Arthur. None the less, they are responsible for a good deal of romantic inspiration. The anonymous medieval writer of The Folie Tristan said that the castle was built by giants and that it used to vanish twice a year - at midwinter and again at midsummer. Thomas Hardy visited and later drew the castle from memory, reinstating its medieval might. Sir Arnold Bax (1883-1953) composed a wonderful tone-poem evoking the majesty and mystery of the place in 1917; to listen to it is to hear the waves crashing against the rocks below the castle.

A much earlier monastic site on the island promontory behind the castle dates from a time more or less contemporary with Arthur. More recent discoveries, following excavations in 1994, indicate that it may have been a Celtic site of some importance. The most recent thinking suggests that there may well be something in the legends surrounding the place.