Glastonbury Tor is a hill near Glastonbury in the English county of Somerset, topped by the roofless St Michael's Tower, a Grade I listed building. The entire site is managed by the National Trust and has been designated a scheduled monument. The Tor is mentioned in Celtic mythology, particularly in myths linked to King Arthur, and has several other enduring mythological and spiritual associations.
The conical hill of clay and Blue Lias rises from the Somerset Levels. It was formed when surrounding softer deposits were eroded, leaving the hard cap of sandstone exposed. The slopes of the hill are terraced, but the method by which they were formed remains unexplained.
Archaeological excavations during the 20th century sought to clarify the background of the monument and church, but some aspects of their history remain unexplained. Artefacts from human visitation have been found, dating from the Iron Age to Roman eras. Several buildings were constructed on the summit during the Saxon and early medieval periods; they have been interpreted as an early church and monks' hermitage. The head of a wheel cross dating from the 10th or 11th century has been recovered.