The conical shape of Glastonbury Tor is natural. Thousands of years ago it was an island. Before modern drainage, the Tor in winter would have towered above the flooded Somerset Levels. The terracing on the hillside has been dated to Neolithic times, around the same time as when Stonehenge was constructed. It has been suggested that the terraces form a kind of maze that guided pilgrims up the sacred hill.
The hill has a long religious history with evidence of Pagan and early Christian settlement on it. If you walk to the top of of it today you will find the partial ruins of a church. The top of the Tor was levelled at some point in the 10th or 11th century to build a large stone church. In 1275 an earthquake levelled this church. A smaller church was rebuilt on the site in 1323 and lasted until the demise of Glastonbury Abbey in 1539. The church was quarried for stone and now only the tower survives.
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Excavations on the Tor have revealed some Neolithic flint tools and Roman artifacts, indicating use since ancient times. The terracing on the side of the hill, if man-made, may also date from the Neolithic era. The first monastic Church of St. Michael that stood on Glastonbury Tor was probably destroyed in the major earthquake of 1275. The church was rebuilt in the 14th century, and only the tower still stands today.
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During the late Saxon and early medieval period, there were at least four buildings on the summit. The base of a stone cross demonstrates Christian use of the site during this period, and it may have been a hermitage. The broken head of a wheel cross dated to the 10th or 11th centuries was found partway down the hill and may have been the head of the cross that stood on the summit. The head of the cross is now in the Museum of Somerset in Taunton. The earliest timber church, dedicated to St Michael, is believed to have been constructed in the 11th or 12th centuries; from which post holes have since been identified. Associated monk cells have also been identified.
St Michael’s Church was destroyed by an earthquake on 11 September 1275. According to the British Geological Survey, the earthquake was felt in London, Canterbury and Wales, and was reported to have destroyed many houses and churches in England. The intensity of shaking was greater than 7 MSK, with its epicentre in the area around Portsmouth or Chichester, South England. A second church, also dedicated to St Michael, was built of local sandstone in the 14th century by the Abbot Adam of Sodbury, incorporating the foundations of the previous building. It included stained glass and decorated floor tiles. There was also a portable altar of Purbeck Marble; it is likely that the Monastery of St Michael on the Tor was a daughter house of Glastonbury Abbey. In 1243 Henry III granted a charter for a six-day fair at the site. St Michael’s Church survived until the Dissolution of the Monasteries in 1539 when, except for the tower, it was demolished.