At 39.3 metres (129 ft) high,[1] the hill is the tallest prehistoric man-made mound in Europe[2] and one of the largest in the world; it is similar in volume to contemporary Egyptian pyramids.

Several other important Neolithic monuments in Wiltshire, including the large henges at Marden and Salisbury Plain (Stonehenge), may be culturally or functionally related to Avebury and Silbury.

Composed mainly of chalk and clay excavated from the surrounding area, the mound stands 39.3 metres (129 ft) high[a] and covers about 2 hectares (5 acres).

Archaeologists calculate that it took 18 million man-hours, equivalent to 500 men working for 15 years[7] to deposit and shape 248,000 cubic metres (324,000 cu yd) of earth and fill.

Euan MacKie asserts that no simple late Neolithic tribal structure as usually imagined could have sustained this and similar projects, and envisages an authoritarian theocratic power elite with broad-ranging control across southern Britain.

[12][10] Silbury Hill was originally entirely white since it had a chalk (limestone) exterior, and the surrounding ditch may have been regularly filled with water from underground springs.

[b] In October 1776, a team of Cornish miners overseen by the Duke of Northumberland and Colonel Edward Drax sank a vertical shaft from the top.

[14] Brian Edwards argues that Drax and his friends—all members of Mrs. Millers' poetry set in Batheaston—were interested in Silbury Hill, because they thought it paralleled the Greek legends of Apollo killing Python, the monstrous snake that lived in the Caves of Parnassus.

[18] In May 2007, contractors Skanska, under the overall direction of English Heritage,[9] began a major programme of stabilisation, filling the tunnels and shafts from previous investigations with hundreds of tonnes of chalk.

On the basis of this survey, it would appear that Neolithic mound-building was restricted to the upper Kennet and Avon valleys, and that nothing extant elsewhere in Britain comes close as a comparison to Silbury Hill.

[23] Few prehistoric artifacts have been found on Silbury Hill: at its core there is only clay, flints, turf, moss, topsoil, gravel, freshwater shells, mistletoe, oak, hazel, sarsen stones, ox bones, and antler tines.

A local legend noted in 1913[24] states that the Devil was carrying a bag of soil to drop on the citizens of Marlborough, but he was stopped by the priests of nearby Avebury.

John C. Barret asserts that any ritual at Silbury Hill would have involved physically raising a few individuals far above the level of everyone else, where they would have been visible for miles around and from several other monuments in the area.

[27] Paul Devereux observes that Silbury and its surrounding monuments appear to have been designed with a system of inter-related sightlines, focusing on the step several metres below the summit.

[28] The hill's vegetation is species-rich chalk grassland, dominated by upright brome and false oat-grass, but with many species characteristic of this habitat, including a strong population of the rare knapweed broomrape.