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Salisbury Plain, Wiltshire, UK
associated engineer
Not known
date  circa 3100 - 2800 BC
era  Pre-Roman  |  category  Monument, historical  |  reference  SU121422
ICE reference number  HEW 248
photo  © Pam Brophy and licensed for reuse under this Creative Commons Licence
Stonehenge is the best known megalithic stone circle in Britain and probably our most important prehistoric monument. The stones remaining on Salisbury Plain today are the final part of a construction that began some 5,000 years ago. Stonehenge was designated a World Heritage Site in 1986.
There have been many theories concerning the purpose of Stonehenge, and no doubt there will be many more. The site may have had religious significance, and it certainly had astronomical connections with sunrise and sunset. Current thinking seems to be that the site is some kind of memorial monument.
The first stage of construction consisted of earthworks, built by Neolithic people around 3100-2800 BC. They made a circular henge consisting of a bank with an outer ditch. Inside the henge is an 87m diameter ring of 56 round pits in the chalk of the site. These are known as 'Aubrey Holes' and each is about one metre deep and one metre wide.
A timber monument was erected some time 2900-2600 BC. After that the site was abandoned for centuries, until the Beaker people constructed the astonishing third and fourth stages.
In the third stage, dating from around 2150-2100 BC, 82 bluestone blocks were transported 386km to the site from the Preseli Hills in south Wales. This is the nearest source of the igneousrock known as bluestone. Each piece, weighing 4-5 tonnes, had to be hewn from the rock face, hauled on sledges and rollers from the quarry to Milford Haven and loaded onto rafts.
The rafts travelled along the Welsh coast and up the Rivers Avon and Frome. The stones were again moved over land to near Warminster, then by water to the River Avon at west Amesbury, some 2km from the site. The bluestones were arranged in a double circle inside the existing earthworks. The entrance to the earthwork henge was widened and a pair of heel stones set up.
Around 2000 BC, in the fourth stage of Stonehenge’s construction, 30 sarsen stones (silicified sandstone) were dragged on sledges (presumably) from Marlborough Downs near Avebury, 40km away. These huge stones weigh around 20 tonnes. The largest is 7.3m high and weighs 45-50 tonnes.
The sarsens were shaped, dressed to a curve of some 15m radius and set vertically in a circle. They have pointed lower ends, enabling them to fit into sockets cut into the chalk. Tenons cut into their top surfaces received mortises on the 7 tonne 'tongue and grooved' sarsen lintels, also dressed to the 15m radius. The lintels formed a continuous ring atop the standing stones when all were in place.
Inside the stone circle, five trilithons, or pairs of uprights with a lintel across each, made from the largest sarsen stones were arranged in a horseshoe shape. The remains of these trilithons can still be seen.
In the fifth and final stage, soon after 1500 BC, the bluestones were moved from their original positions into the sarsen circle and placed in the horseshoe arrangement that exists now.
Estimates of the phenomenal effort required to build Stonehenge suggest that it would have taken more than 30 million hours of labour. Moving just one of the sarsen stones would have needed around 600 men.
Stonehenge is maintained by English Heritage and is surrounded by 600 hectares of National Trust land. The site is open to the public, although access to the stone circle is restricted to pre-booked out-of-hours visits for small groups.
Research: ECPK
"A Concise History of England from Stonehenge to the Atomic Age"
by F.E. Halliday, Thames and Hudson, London, 1964
reference sources   CEH South