The Engineering of Stonehenge

Learn about the engineering and architecture of Stonehenge, Britain’s most famous prehistoric monument.

Article By: Francesca Burke
Last Update: November 2018

Stonehenge, a ring of standing stones in Wiltshire, England, is one of Britain’s most famous prehistoric monuments and a World Heritage Site. Located about 90 miles from London and 2 miles from the town of Amesbury, today Stonehenge is revered as an icon of the British countryside. It’s also famous as a spectacular feat of engineering: it is the only surviving lintelled stone circle in the world.

Origins of Stonehenge

It’s believed that Stonehenge was first used as a cremation ceremony site. Originally built around 3,000 BCE as an earthen circular enclosure reinforced with 56 stone or timber blocks, the ditch was dug using antler tools! The area was used for cremations for several hundred years.

Constructing the Stone Circle

In the late Neolithic period, around 2500 BCE, the famous stones were added after a great deal of organised effort. Stonehenge consists of large sandstone blocks called sarsens and smaller ‘bluestones’ (so-called because they have a bluish tinge when freshly broken or wet).

Initially, the sarsens formed an inner horseshoe and an outer circle, while the bluestones were set up between them in a double arc. 200 or 300 years later the bluestones were rearranged to form a circle and inner oval (which was again later altered to form a horseshoe).

Bird's eye view down on to the Sarsen Circle at Stonehenge

A bird’s eye view of the interlocking sarsens, from Historic England

Stonehenge’s main stones were raised upright by first digging a hole with a sloping side. The back of the hole was lined with wooden stakes, then the stone was moved into position and hauled upright using plant-fibre ropes and most likely a wooden A-frame (weights may have helped tip the stone upright). The hole was then packed with rubble. The horizontal stones were probably raised using timber frames, with the vertical and horizontal stones slotted together using mortice holes and tenons.

To get a better idea of the stages of constructing Stonehenge, download English Heritage’s plan showing each phase of construction.

mortice and tenon joints used in Stonehenge illustration by Peter Dunn for Historic England

Illustration by Peter Dunn © Historic England

 What makes Stonehenge such a feat of engineering is that although sarsens are found naturally across southern England, archeologists estimate that the sarsens at Stonehenge are from the Marlborough Downs, 20 miles away! They weigh on average 25 tons, so the builders would have devised a way to drag the stones manually. The bluestones came from the Preseli Hills in south-west Wales. The bluestones weigh between 2 and 5 tons, and once again would have been dragged or carried manually by workers.
It’s still not known exactly how the stones were moved: one theory is that they were carried via water networks, while another theory suggests that workers constructed tracks of logs and rolled the stones along! Interestingly, research has shown that some of the people cremated at Stonehenge were originally from the Preseli Hills, which suggests that the people who constructed Stonehenge moved permanently to the site along with the stones.

Stonehenge’s Purpose

Adding to the mystery of Stonehenge is that its purpose has been disputed. Theories have included it as a coronation place for Danish kings, an astronomical computer, a Druid temple and a Roman temple.

Today it’s generally agreed that Stonehenge was aligned with the movements of the sun. The main axis of the stones is aligned upon the solstitial axis, and at midsummer, the sun rises close to the ‘Heel Stone’, a large sarsen stone outside the entrance to the Stonehenge earthwork. At midwinter, the sun sets in the gap between the two tallest trilithons. The seasonal cycles were clearly important to the builders of Stonehenge, but we may never know exactly what its intended purpose was.

STONEHENGE View from the North East at sunrise

North East of Stonehenge, from Historic England

We hope you found this post interesting. Are you interested in architecture and engineering? Why not check out our blogs about other famous buildings?

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