Tintagel Castle is the birth place of King Arthur. Honest. Ok, in reality, whatever that is, the Castle isn't old enough to be Arthurian, but, in reality, it's the perfect setting. Built on the edge of a windswept cliff, with the ocean pounding at it's base, one can imagine Uther Pendragon entering the Castle at night to seduce Igraine, wife of Gorlois of Cornwall, which resulted in the birth of Arthur.
To get to Tintagel, one must park and walk down a valley, to the visitor's center, then climb many, many, many uneven steps, carved into the side of the cliffs, before finally reaching the entrance of the castle. But it is worth it; the setting is huge, even by castle standards, and the view is spectacular!