Dominating the surrounding landscape, the steep and isolated hill which is Glastonbury Tor is visible for twenty miles in every direction. The abbey that was located here was a Christian site, the tor in legend is the entrance to the fairy underworld.
The story of this, however, is not very ancient or even possibly true. A 16th century Welsh text Life of St. Collen has the story within, but it is possible he never existed as there is no other records of his existence. (Maybe he got lost in fairyland)
The story relates that Collen came to 'the mountain of Glastonbury' and settled as a hermit in a quiet spot amongst the rocks. One day he overheard two locals talking about Gwynn ap Nudd, King of the Fairies and the Lord of Annwn, King of the Underworld who both lived on that very hill. Collen rebuked them for believing in fairies which he claimed were simply demons.
Gwynn, apparently offended, summoned Collen three times to meet him on the top of the tor at midday; eventually Collen reluctantly agreed, but brought a flask of holy water with him.
And when he came there he saw the fairest castle he had ever seen, and around it the best appointed hosts, and many musicians with every instrument and string music, and horses with boys on their backs, the fairest in the world, and girls of noble aspect, lively activity, light footed, lightly dressed, in the flower of young age, and every dignity that was known to the court of a powerful king; and he saw a fine man on top of the fortress bidding him to come in, and saying that the king was awaiting him for his dinner.
He was then brought to where Gwynn ap Nudd was enthroned on a golden chair and offered fine food and drink, which he refused. Gwynn boasted of his courtiers particolored clothing, red on one side, blue on the other. "Their dress is good of its kind, " answered Collen, "but the red is that of flames, and the blue that of ice." Referring to the medieval belief that Hell had both ice and fire. He then sprinkled the holy water, and everything disappeared, leaving the saint standing among the grassy mounds on the bleak hilltop.