Silbury Hill

51.4157°N, 1.8574°W.

Silbury Hill near Avebury in Wiltshire, England — the largest prehistoric artificial mound in Europe, built between approximately 2470 and 2350 BCE during the late Neolithic. Original base 167 metres per side; original height 39.6 metres in a stepped chalk-rubble mound faced with chalk-block revetments. Construction is estimated to have required 4 million man-hours and approximately 248,000 cubic metres of chalk and clay, all moved by hand and antler-pick. Excavated through tunnels in 1776 (by the Duke of Northumberland's miners), 1849 (by John Merewether), 1968–70 (by Richard Atkinson for the BBC), and again in 2007–8 by English Heritage. None of the excavations recovered a burial, a chamber, or any artefact identifying a function — the mound appears to have been built solid, with no internal structure. The 1776 and 1968 tunnels were stabilised by English Heritage in 2007 after partial collapse of the upper portions.

The largest prehistoric mound in Europe, with no burial and no documented purpose, in a Wiltshire landscape that includes Stonehenge 25 kilometres south and Avebury 1.5 kilometres north.