Silbury Hill rises abruptly from the Kennet valley near Avebury: a huge grass-covered mound built by people in the late Neolithic. Its scale is easy to measure. Its meaning is not. More than four thousand years after construction, archaeologists can describe how it grew in remarkable detail without being able to say with confidence why it was built.

Built, enlarged, built again

English Heritage describes Silbury Hill as the largest artificial prehistoric mound in Europe. It stands about 30 metres high and roughly 160 metres wide, and around half a million tonnes of material — much of it chalk — went into its construction.

Research now shows that the monument developed through repeated episodes rather than appearing in one simple building campaign. Work probably took place between about 2470 and 2350 BC, beginning with much smaller deposits and mounds before successive enlargements transformed the site.

CONSTRUCTION · late Neolithic, cumulative and multi-phase

Part of the Avebury world

Silbury was not an isolated project. It belongs to the extraordinary prehistoric landscape around Avebury, alongside the henge and stone circles, avenues, West Kennet monuments and other late Neolithic activity.

The amount of labour involved implies sustained organisation and repeated communal effort. But that does not give us a safe single explanation for the mound. English Heritage is explicit that its original purpose and meaning remain unknown.

INTERPRETATION · context is strong; purpose remains unresolved

Not the tomb people expected

Later investigators repeatedly went looking for answers inside the mound. A vertical shaft was sunk from the summit in 1776, a horizontal tunnel was driven in during 1849, and another major tunnel excavation followed in 1968–70.

None produced the central burial treasure hunters had hoped for. Evidence instead revealed a complicated construction history, while later survey showed Roman activity around the foot of the hill and possible early-medieval modification of the summit.

RESEARCH HISTORY · repeated excavation changed what we know — and physically damaged the monument

When archaeology became a conservation problem

The old tunnels were not fully backfilled. In 2000 a deep crater opened on the summit and investigations showed voids and collapsing passages inside the mound.

A major conservation project followed. In 2007 archaeologists took a final opportunity to record deposits inside the reopened tunnel before known voids and the summit crater were refilled with chalk. The work stabilised the monument and produced new dating and environmental evidence about how Silbury was constructed.

CONSERVATION · modern research was tied directly to repairing earlier excavation damage

A monument to look at, not climb

Silbury Hill is a Scheduled Monument within the Avebury part of the Stonehenge, Avebury and Associated Sites World Heritage landscape. English Heritage states that there is no public access onto the mound itself because of the sensitive archaeology.

That restriction suits the deeper story. Silbury is compelling precisely because so much survives in the structure: layers of chalk, soil, turf and biological material that still hold evidence about the people and landscape that created it.

PROTECTION · sensitive archaeology remains inside the mound

Sources & provenance

  1. English Heritage — History of Silbury Hill
  2. English Heritage — Research on Silbury Hill
  3. English Heritage — Silbury Hill, Avebury
  4. English Heritage — The Avebury World Heritage Site
  5. Historic England — Silbury Hill, Scheduled Monument 1008445

Image note: Website lead image is a genuine 6 August 2017 photograph of Silbury Hill by Stevekeiretsu, published on Wikimedia Commons under CC BY-SA 4.0. It is used as documentary place imagery.

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