Arthur has always been a big deal associated with Glastonbury for 800 years, though today there are no physical remains of him or his queen in the tomb. The Lady Chapel was built over the remains of first church after it burnt down, though the walls of the old church still remain standing. They reconstructed the tomb so people that visited would understand how the tomb look as it was discovered. Finding this tomb was apparently the first evidence that Glastonbury was the isle of Avalon. The bone where then moved to the south isle of the church, and later moved to the black marble mausoleum in front the high alter.
In this article it details the abbey a lot. It reflects on the history of Joseph and King Arthur and how they built the Abbey. It also tells a lot of information on jesus and how the church burnt down. Not only does it tell that, it also tells what you can see today if you go visit the new church that is built over the old Glastonbury Abbey.