There is a tower on Glastonbury Hill, which is the remains of a church that once stood here.

An excerpt from the article 16 facts about Glastonbury

According to legend, the hill was the entrance to Avon, a hidden kingdom of the underworld. In the 6th century, Saint Kolin visited the hill of Tor, entered through a hidden entrance, and found himself in a magnificent palace. He sprinkled everything with holy water, which caused the palace to disappear.