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.[2] 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.