A site in Wiltshire, England, at which stands one of Britain's finest megalithic monuments (known as henges) and one of the largest ceremonial structures in Europe. It was built c 2000 BC in the Neolithic, where the ridgeways of southern England meet, a natural site for tribal gatherings. It consists of a large bank with internal ditch (1.2 km long) with four equally spaced entrances. Inside the ditch was set a circle of 98 sarsen stones, weighing as much as 40 tons each. In the center were two smaller stone circles, each c 100 meters in diameter. The northern circle contains a U-shaped setting of three large stones, and the southern inner circle once had a complex arrangement of stones at its center. The Ring Stone, a huge stone perforated by a natural hole, stood within the earthworks and main stone circle at the southern entrance. The southern entrance leads out to two parallel rows of sarsens forming an avenue 15 m wide and 2.5 km long which ends at a ritual building (the so-called Sanctuary) on Overton Hill. Traces of a second avenue remain on the opposite side of the monument. From the bottom of the ditch came sherds of Neolithic Windmill Hill, Peterborough, and Grooved Ware styles, while higher up were fragments of South British (Long Necked) Beaker and Bronze Age pottery. Burials with Beaker and Rinyo-Clacton wares have been excavated at the bases of some of the stones. Near the southern end of the Avenue was an occupation site with Neolithic and Beaker sherds. The complex geometry of the site is studied, especially the possible astronomical alignments built into it. The circles at Avebury and the wooden structure on Overton Hill were all probably built at the same time by Neolithic communities.