Tintagel is an English castle, currently in ruins, located near the village of Tintagel in Cornwall.
Tintagel is one of the places that King Arthur Pendragon and Griff visit in their search for Merlin.  (In "Rock & Roll", Arthur stated that he and Griff had already searched for Merlin in "all the obvious places", but it is unclear whether or not that included Tintagel.)
Real World Background
In Arthurian legend, Tintagel is best known as the site of Arthur Pendragon's conception. Arthur's father, Uther Pendragon, became obsessed with Igraine, the wife of Duke Gorlois of Cornwall. Aware of Uther's feelings for his wife, Gorlois fled with her to Cornwall; Uther ordered Gorlois to return to court, and when Gorlois refused, declared war on him and invaded Cornwall. Gorlois locked Igraine away in Tintagel to keep her safe, while taking up his headquarters in a castle variously known as Dimilioc or Castle Terrabil. After besieging Gorlois in vain for a week, Uther sought the help of Merlin, who transformed him into the likeness of Gorlois, allowing him to enter Tintagel and spend the night with Igraine, thereby conceiving Arthur. (While the medieval versions of the story portray Igraine as deceived, some modern versions have made her aware of Uther's true identity and willingly admit him to her bed.) The real Gorlois took advantage of Uther's absence to make a sortie and attack his leaderless army; he was slain in the subsequent fighting, thus allowing Uther to marry Igraine afterwards.
Arthur is only conceived at Tintagel in the medieval versions; the notion that he was born there seems to have been a later invention.
The facts of Arthur's parentage and conception in the Gargoyles Universe have not yet been revealed, so it is impossible to say which - if any - of the tales surrounding Tintagel are accurate.
Archaeologists believe that Tintagel was originally a Roman fort built during the third or fourth century. After the departure of the Romans, the site was home to a Celtic fortress. The actual castle was not built until 1233 by Richard, Earl of Cornwall. Richard had the castle built in an older style to help associate it with the legends of Arthur and the Cornish kings in hopes of winning favor with the people of Cornwall. Subsequent earls had little interest in the castle and allowed it to fall into ruin. The Victorian era saw a renewed interest in the tales of King Arthur, turning Tintagel from a forgotten ruin into a popular tourist destination.
Greg Weisman visited Tintagel in 1981 and in 1992 with his family. On Ask Greg, he has written that on both occasions he felt a rush and that it was as if the ground "was charged with some kind of power". 
- Tintagel at Wikipedia, the Free Encyclopedia