Chalk and earth mound near Avebury, Wilts, constructed between 2400 and 2300 BCE
Silbury Hill is a conical, flat-topped Neolithic mound located a short distance from Beckhampton, Wilts (map reference SU100685). It is the largest man-made prehistoric mound in Europe, standing 130ft (40m) high and 550ft (167m) in diameter, and covering 5 acres (2.2 hectares). Located in a region rich with Neolithic monuments, it is believed to be 4750 years old. Its purpose is unknown. It is composed principally of chalk excavated locally. Some 8.75 million cubic feet (248,000 cubic metres) of material went into its construction. It has been calculated that it took 18 million work-hours to construct; the equivalent of 500 men working for 15 years. This suggests social complexity had evolved beyond the tribal level, as only a powerful ruling elite could have mustered the resources for such a project.