Read this: In Arthurian legend, Avalon became associated with Glastonbury Tor when monks at Glastonbury Abbey claimed to have discovered the bones of King Arthur and his queen. What is more certain is that Glastonbury was an important religious centre by 700 and claims to be "the oldest above-ground Christian church in the World" situated "in the mystical land of Avalon." The claim is based on dating the founding of the community of monks at AD 63, the year of the legendary visit of Joseph of Arimathea, who was supposed to have brought the Holy Grail. During the Middle Ages there were also important religious sites at Woodspring Priory and Muchelney Abbey. The present Diocese of Bath and Wells covers Somerset – with the exception of the Parish of Abbots Leigh with Leigh Woods in North Somerset – and a small area of Dorset. The Episcopal seat of the Bishop of Bath and Wells is now in the Cathedral Church of Saint Andrew in the city of Wells, having previously been at Bath Abbey. Before the English Reformation, it was a Roman Catholic diocese; the county now falls within the Roman Catholic Diocese of Clifton. The Benedictine monastery Saint Gregory's Abbey, commonly known as Downside Abbey, is at Stratton-on-the-Fosse, and the ruins of the former Cistercian Cleeve Abbey are near the village of Washford.
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): What is built in Avalon
the oldest above-ground Christian church in the World" situated "in the mystical land of Avalon