The Neolithic Windmill Hill monument encloses an area of 8.45 hectares, making it one of the largest in England; it was also one of the first to be recognised as a causewayed `camp' or enclosure. The finds have been important to establishing the extent of transport of artefacts and materials during the early Neolithic, the nature of early farming, and the development of pottery styles. The enclosure has three circuits, defined by the inner, middle and outer ditches. The smallest, inner ditch has no trace of a bank, and the north-west part probably had an entrance. The middle ditch is circular, may have traces of an inner bank, and a possible entrance in the form of a wide causeway, slightly offset from the entrance in the inner ditch. The largest, outer ditch has a bank which in parts survives to 0.7 metres high and 5 metres wide. The site was excavated by H G O Kendall in 1922-23, Alexander Keiller in 1925-29, I F Smith in 1957-58, and A Whittle in 1990. The finds included Neolithic flint artefacts such as arrowheads, axe-heads, a sickle blade and scrapers. Numerous animal bones and skulls as well as 'ceremonial chalk cups' were also found. A type of Neolithic pottery found on sites across Wessex was first identified here and has hence taken the name of the site: Windmill Hill type pottery. A radiocarbon dating programme now places construction between 3700-3601cal BC, and the continuation of its main use until about 3500 or 3300 cal BC, with the construction of the monument as a whole taking place over the span of just one or two generations.
The date and the location in the Avebury area associate it with the origins of a unique monument complex, of which the earliest elements may have been some of the nearby long barrows. Later additions included Silbury Hill, the Avebury complex, the Longstones enclosure, and the West Kennet Farm enclosures. In the Early Bronze Age, round barrows were built on the hill itself and on the slope to the south.