Stonehenge

Stonehenge is the most analysed, most written about, and most visited prehistoric monument in the world, and it remains, after two centuries of scientific investigation, genuinely mysterious. Not in the sense of being inexplicable — archaeologists and astronomers have established a great deal about how it was built, when it was built, and what astronomical alignments it encodes — but in the deeper sense that the society that built it left no written record and the belief system that motivated its construction must be reconstructed entirely from physical evidence whose meaning is ultimately opaque. We know what Stonehenge is. We do not know, and may never know with certainty, what Stonehenge meant.

What it is, physically, is a series of concentric stone settings on an open chalk downland in Wiltshire, approached by a ceremonial avenue that runs northeast from the monument toward the Avon River. The outer circle consists of large sarsen sandstone uprights capped by continuous lintels, a post-and-lintel construction of considerable engineering difficulty given the weight of the stones and the absence of metal tools or wheeled transport. Within this outer circle are trilithons, pairs of uprights with single lintels set in a horseshoe arrangement, the largest reaching over 7 metres in height. Between and within these sarsen settings are smaller bluestones, brought from the Preseli Hills in Wales over 200 kilometres away, an act of stone transportation at a scale that continues to generate research and debate.

The monument does not stand alone. It is the most visible element of a much larger ceremonial landscape that has been accumulating monuments, earthworks, burial mounds, and ritual features for over five thousand years. The Stonehenge World Heritage Site encompasses approximately 2,600 hectares of Wiltshire downland containing hundreds of individual heritage features, from the Neolithic causewayed enclosures that predate Stonehenge by centuries to the Bronze Age barrow cemeteries that accumulated around it over a millennium after its completion.

Stonehenge is significant at multiple levels simultaneously. As an engineering achievement it is remarkable — the quarrying, transport, and erection of stones weighing up to 25 tonnes, some from sources over 200 kilometres away, using only the technology available to Neolithic and early Bronze Age communities, represents a logistical and organisational feat that continues to be studied and debated. As an astronomical instrument it is precise — the principal alignment with the midsummer sunrise and midwinter sunset has been confirmed by archaeoastronomers and was clearly intentional. As a cultural landscape it is extraordinarily rich, the accumulated monuments of the wider World Heritage area representing five millennia of human religious activity in a single landscape.

Its significance for contemporary culture is also substantial, though more complex. Stonehenge has been claimed as a symbol by British nationalism, by the Romantic movement, by neo-druidic religious groups, by the New Age movement, and by the heritage tourism industry, each of which has projected different meanings onto the monument's ambiguity. The site's capacity to absorb these projections without resolving them is part of what makes it culturally powerful, and also part of what makes its management contentious.

Infrastructure and the A303

The proposed tunnel beneath the A303 road is both a potential benefit and a genuine threat, depending on how it is designed and implemented. The unexcavated archaeological deposits along the tunnel route are genuine and significant, and the concern that construction would cause irreversible damage to buried heritage is legitimate. At the same time, the current situation — with heavy traffic running in a cutting within the World Heritage Site — is itself an ongoing impact on the monument's setting and on the physical condition of archaeological deposits through vibration and pollution.

Mass Tourism

Approximately 1.6 million people visit Stonehenge annually. The visitor management infrastructure developed over the past decade, with the new visitor centre and restricted access to the stone circle itself, has significantly reduced the physical impact of visitor pressure on the monument. The experience of being at Stonehenge is still, for most visitors on most days, defined by the presence of large numbers of other people, which diminishes the experiential quality without necessarily causing physical damage.

Climate Change

The chalk downland of the Stonehenge landscape is sensitive to hydrological changes, and the increasing frequency of extreme rainfall events is affecting the drainage patterns and erosion rates of the monument and its surrounding earthworks. The sarsen stones are geologically robust, but the buried archaeological deposits within the World Heritage Site are sensitive to changes in soil moisture regimes.

Biological Growth

Lichen and other biological growth on the sarsen surfaces is a continuous conservation management challenge. Some level of biological coverage is aesthetically accepted and practically difficult to prevent on outdoor stone in a temperate climate, but accelerating biological growth in response to climate change could affect the stone surfaces at rates that require more active intervention.

Stonehenge has attracted more archaeological investigation per square metre than almost any other site in the world, and the cumulative research has produced a picture of the monument and its landscape that is considerably more complex and more interesting than the iconic image of a stone circle on a windswept plain suggests.

The Stonehenge Riverside Project, led by Mike Parker Pearson, transformed understanding of the monument by demonstrating that Stonehenge was the focus of a much larger ceremonial complex connected by the Avenue to the river Avon and by the river to Durrington Walls, a large timber circle 3 kilometres away, where the living gathered. Parker Pearson's interpretation of Stonehenge as a monument to the dead, connected to a place for the living, situated within a landscape organised around the movement between life and death that the river represented, is not universally accepted but has substantially reframed the questions researchers ask about the site.

Research into the provenance of the bluestones using geochemical analysis has identified the specific outcrops in the Preseli Hills from which individual stones were quarried, and associated research has found evidence of earlier stone circles in Wales that may have been dismantled and transported to Stonehenge — suggesting that the stones themselves carried accumulated sacred significance from previous use.

Stonehenge is in less acute danger than many sites in this series, and the conservation infrastructure around it is more developed and better resourced than most. The primary risks are diffuse and cumulative: the slow effects of climate change on buried deposits, the compounding impact of years of visitor pressure, and the unresolved question of what to do about the A303.

The risk that is hardest to quantify is the one posed by the infrastructure debate. The construction of the proposed tunnel, if it proceeds in a form that causes significant damage to unexcavated deposits within the World Heritage Site, could destroy archaeological evidence that no amount of subsequent investigation could recover.

Stonehenge has been asking the same question for five thousand years and has not yet received an answer: what made this place sacred, and what does the persistence of that question say about the human need for it? Protecting the site means protecting not just the stones but the unexcavated landscape around them, the buried deposits that still contain evidence we do not yet have the tools to fully interpret. That is a case for caution, for patience, and for the kind of long-term institutional commitment that the site's five-thousand-year history demands.