The isle of avalon was said to be located in Glastonbury. People associate the two places and say that the entrance to avalon or the Celtic underground is marked by the church.(1)
Queen Guinevere, after her adulteress relations with sir lancelot, went and became a nun in the church at glastonbury. (2)
Avalon comes from the British word lava, meaning apples. Therefore, the Isle of Avalon means "The Island of Apples." Excalibur, King Arthur's sword, was made on the Isle of Avalon. It was also where Arthur retreated to after he was mortally wounded by Mordred. The Isle of Avalon is also tied to many other British legends. (3)
Adam and eve picked the forbidden fruit from the tree of knowledge of good and evil(5) it is commonly thought that that fruit was an apple (although in the bible they never say) in celtic tales an apple tree is the tree of life, and "bears the fruit of immortality which emits a heavenly fragrance, is able to satisfy all hunger, heal all ills, and yet always remains whole." (6)
The Welsh word for the Isle of Avalon was Ynys Avallach, which means The Island of Apples. Apples in the Celtic tradition symbolizes magic. (4)
(3)
(1)http://www.britannia.com/history/arthur/avalon.html
(2)Mists of avalon, Marion Zimmer Bradley
(3) http://csis.pace.edu/grendel/projs993a/arthurian/avalon.htm
(4)http://www.bardsongpress.com/avalon.htm
(5) the bible
(6)http://www.avalonmysteryschool.net/inneravalon.htm