Glastonbury Tor is a high teardrop-shaped hill at Glastonbury, Somerset, England, with its only standing architectural feature the roofless St Michael's Tower of the former church. 'Tor' is a local word of Celtic origin meaning 'conical hill'. The tor has a striking location in the middle of a plain called the Summerland meadows , part of the Somerset Levels. The plain is actually reclaimed fenland, out of which the tor rose like an island, but now, with the surrounding flats, a peninsula washed on three sides by the river Brue. The remains of a lake-village were identified in 1892, showing that there was a Celtic settlement about 300 - 200 BC, on what was an easily defended island in the fens. Earthworks and Roman remains prove later occupation. The spot seems to have been called Ynys yr Afalon by the Britons, and it is widely believed to be the Avalon of Arthurian legend.

The slopes of the tor appear to be quite regularly terraced. Some believe that this formation is the remains of an ancient, perhaps neolithic, sacred labyrinth, while others attribute the terraces to natural ruts formed everywhere on grassy slopes by generations of grazing animals, which are slow to disappear if the grass cover is left undisturbed. The most likely explanation is medieval strip farming. Even after the wetlands were drained by the Monks of Glastonbury Abbey, by their vast network of drainage canals, the risk of flooding on the plain meant that farm land was at a premium, for anything other than grazing cattle.

The tor is managed by The National Trust.

History

Some neolithic flint tools recovered from the top of the Tor show that the site has been visited and perhaps occupied throughout human prehistory. Excavations on Glastonbury Tor, undertaken between 1964 and 1966, revealed evidence of Dark Age occupation around the later Medieval church of St. Michael: postholes, two hearths, one of them a metalworker's forge, two burials oriented north-south (thus unlikely to be Christian) and fragments of 6th century Mediterranean amphorae (for wine or oil). A worn hollow bronze head may have topped a Saxon staff. The Celtic name of the tor was "Ynis Witrin", meaning "Isle of Glass". At this time the plain was flooded, the isle becoming a peninsula at low tide.

Remains of a 5th century fort have been found on the tor. This was replaced by the medieval St. Michael's church that remained until 1275. A second church, built in the 1360s, survived until the Dissolution of the Monasteries in 1539, when the Tor was the place of execution of the last Abbot of Glastonbury Abbey. The remains of St. Michael's Tower were restored in modern times.

The site of the fair held at the foot of the Tor is embodied in the traditional name of "Fair Field" given to an agricultural enclosure, the enclosures in the local landscape dating from the 18th century.

• Archaeology on the Tor
• National Trust conservation statement, 1999: topography, archaeology, associative values, policies

Mythology

In Celtic mythology the tor was associated with Gwyn ap Nudd, who was first Lord of the Underworld, and later King of the Fairies. The tor was believed to be an entrance to Annwn or Avalon, the land of the fairies. Later the tor, its 5th century fort, and the name Avalon, became identified with the legendary Celtic hero King Arthur

A persistent myth is that of the Glastonbury Zodiac, an astrological zodiac of gargantuan proportions said to have been carved into the land along ancient hedgerows and track-ways some 2,000 years ago. It is a charming idea, and someone has clearly spent a lot of time poring over maps and crosschecking aerial photographs to support it. Unfortunately, it failed to occur to that person that the vast majority of the land said to be covered by the zodiac was, at the proposed time of its construction, under several feet of water.

Geology

The Tor apparently has been produced by the iron-rich waters of Chalice Well, a spring that has been flowing for millions of years, impregnating the sandstone round it with iron oxides that have reinforced it. Iron-rich, but oxyen-poor water in the aquifer, carries dissolved Iron (II) "ferrous" iron, but as the water surfaces and its oxygen content rises, the oxidized Iron (III) "ferric" iron drops out as insoluble "rusty" oxides that bind to the surrounding stone, hardening it. As the surrounding soft sandstone has eroded away, Glastonbury Tor has slowly been revealed.

• Explanation of the geological origin of Glastonbury Tor
• see also: drumlin