Windmill Hill, Avebury

Windmill Hill is a Neolithic causewayed enclosure in the English county of Wiltshire, part of the Avebury World Heritage Site, about 1 mile (2 km) northwest of Avebury. Enclosing an area of 21 acres (8.5 ha), it is the largest known causewayed enclosure in Britain. The site was first occupied around 3800 BC, although the only evidence is a series of pits apparently dug by an agrarian society using Hembury pottery. During a later phase, c. 3700 BC, three concentric segmented ditches were placed around the hilltop site, the outermost with a diameter of 365 metres. The causeways interrupting the ditches vary in width from a few centimetres to 7 m. Material from the ditches was piled up to create internal banks; the deepest ditches and largest banks are on the outer circuit. In the same period there was also a rectangular mortuary enclosure. The site was designated as a scheduled monument in 1925. It came into the ownership of the National Trust in 1942 and is under the guardianship of English Heritage.