Stonehenge is a prehistoric monument located in the English county of Wiltshire, about 3.2 kilometres (2.0 mi) west of Amesbury and 13 kilometres (8.1 mi) north of Salisbury. One of the most famous sites in the world, Stonehenge is composed of earthworks surrounding a circular setting of large standing stones and sits at the centre of the densest complex of Neolithic and Bronze Age monuments in England, including several hundred burial mounds.[1] Archaeologists had believed that the iconic stone monument was erected around 2500 BC, as described in the chronology below. However one recent theory has suggested that the first stones were not erected until 2400-2200 BC,[2] whilst another suggests that bluestones may have been erected at the site as early as 3000 BC (see phase 1 below). The surrounding circular earth bank and ditch, which constitute the earliest phase of the monument, have been dated to about 3100 BC. The site and its surroundings were added to the UNESCO's list of World Heritage Sites in 1986 in a co-listing with Avebury henge monument, and it is also a legally protected Scheduled Ancient Monument. Stonehenge itself is owned by the Crown and managed by English Heritage while the surrounding land is owned by the National Trust.

New archaeological evidence found by the Stonehenge Riverside Project indicates that Stonehenge served as a burial ground from its earliest beginnings. The dating of cremated remains found that burials took place as early as 3000 B.C, when the first ditches were being built around the monument. Burials continued at Stonehenge for at least another 500 years when the giant stones which mark the landmark were put up. According to Professor Mike Parker Pearson, head of Stonehenge Riverside Project:
“Stonehenge was a place of burial from its beginning to its zenith in the mid third millennium B.C. The cremation burial dating to Stonehenge's sarsen stones phase is likely just one of many from this later period of the monument's use and demonstrates that it was still very much a domain of the dead."

Christopher Chippindale's Stonehenge Complete gives the derivation of the name Stonehenge as coming from the Old English words "stān" meaning "stone", and either "hencg" meaning "hinge" (because the stone lintels hinge on the upright stones) or "hen(c)en" meaning "hang" or "gallows" or "instrument of torture". Medieval gallows consisted of two uprights with a lintel joining them, resembling Stonehenge's trilithons, rather than looking like the inverted L-shape more familiar today.

The "henge" portion has given its name to a class of monuments known as henges. Archaeologists define henges as earthworks consisting of a circular banked enclosure with an internal ditch. As often happens in archaeological terminology, this is a holdover from antiquarian usage, and Stonehenge is not truly a henge site as its bank is inside its ditch. Despite being contemporary with true Neolithic henges and stone circles, Stonehenge is in many ways atypical. For example, its extant trilithons make it unique. Stonehenge is only distantly related to the other stone circles in the British Isles, such as the Ring of Brodgar.

Stonehenge itself evolved in several construction phases spanning at least some 1500 years. However there is evidence of large scale construction both before and afterwards on and around the monument that perhaps extends the landscape's time frame to 6500 years.

Dating and understanding the various phases of activity at Stonehenge is not a simple task; it is complicated by poorly kept early excavation records, surprisingly few accurate scientific dates and the disturbance of the natural chalk by periglacial effects and animal burrowing. The modern phasing most generally agreed by archaeologists is detailed below. Features mentioned in the text are numbered and shown on the plan, right, which illustrates the site as of 2004. The plan omits the trilithon lintels for clarity. Holes that no longer, or never, contained stones are shown as open circles and stones visible today are shown coloured. It is widely assumed that Stonehenge once stood as a magnificent "complete" monument; we should be aware that this cannot be proved, since around half of the stones that should be present are in fact missing, and since many of the assumed stone sockets have never actually been recorded through excavation.

Before the monument (8000 BC forward)

Some archaeologists have found four (or possibly five, although one may have been a natural tree throw) large Mesolithic postholes which date to around 8000 BC nearby, beneath the modern tourist car-park. These held pine posts around 0.75 metres (2 ft 6 in) in diameter which were erected and left to rot in situ. Three of the posts (and possibly four) were in an east-west alignment and may have had ritual significance; no parallels are known from Britain at the time but similar sites have been found in Scandinavia. At this time, Salisbury Plain was still wooded but four thousand years later, during the earlier Neolithic, a causewayed enclosure at Robin Hood's Ball and long barrow tombs were built in the surrounding landscape. In approximately 3500 BC a large cursus monument was built 700 metres (2,300 ft) north of the site as the first farmers began to clear the forest and exploit the area.

Stonehenge 1 (ca. 3100 BC)

The first monument consisted of a circular bank and ditch enclosure made of Late Cretaceous (Santonian Age) Seaford Chalk, (7 and 8) measuring around 110 metres (360 ft) in diameter with a large entrance to the north east and a smaller one to the south (14). It stood in open grassland on a slightly sloping but not especially remarkable spot. The builders placed the bones of deer and oxen in the bottom of the ditch as well as some worked flint tools. The bones were considerably older than the antler picks used to dig the ditch and the people who buried them had looked after them for some time prior to burial. The ditch itself was continuous but had been dug in sections, like the ditches of the earlier causewayed enclosures in the area. The chalk dug from the ditch was piled up to form the bank. This first stage is dated to around 3100 BC after which the ditch began to silt up naturally and was not cleared out by the builders. Within the outer edge of the enclosed area was dug a circle of 56 pits, each around 1 metre (3.3 ft) in diameter (13), known as the Aubrey holes after John Aubrey, the seventeenth century antiquarian who was thought to have first identified them. The pits may have contained standing timbers, creating a timber circle although there is no excavated evidence of them. A recent excavation has suggested that the Aubrey Holes may have originally been used to erect a bluestone circle. If this were the case it would advance the earliest known stone structure at the monument by some 500 years. A small outer bank beyond the ditch could also date to this period.

Stonehenge 2 (ca. 3000 BC)

Evidence of the second phase is no longer visible. It appears from the number of postholes dating to this period that some form of timber structure was built within the enclosure during the early 3rd millennium BC. Further standing timbers were placed at the northeast entrance and a parallel alignment of posts ran inwards from the southern entrance. The postholes are smaller than the Aubrey Holes, being only around 0.4 metres (16 in) in diameter and are much less regularly spaced. The bank was purposely reduced in height and the ditch continued to silt up. At least twenty-five of the Aubrey Holes are known to have contained later, intrusive, cremation burials dating to the two centuries after the monument's inception. It seems that whatever the holes' initial function, it changed to become a funerary one during Phase 2. Thirty further cremations were placed in the enclosure's ditch and at other points within the monument, mostly in the eastern half. Stonehenge is therefore interpreted as functioning as an enclosed cremation cemetery at this time, the earliest known cremation cemetery in the British Isles. Fragments of unburnt human bone have also been found in the ditch fill. Late Neolithic grooved ware pottery has been found in connection with the features from this phase providing dating evidence.

Stonehenge 3 I (ca. 2600 BC)

Archaeological excavation has indicated that around 2600 BC, timber was abandoned in favour of stone, and two concentric arrays of holes (the Q and R Holes) were dug in the centre of the site. These stone sockets are only partly known (hence on present evidence are sometimes described as forming ‘crescents’), however they could be the remains of a double ring. Again, there is little firm dating evidence for this phase. The holes held up to 80 standing stones (shown blue on the plan) only 43 of which can be traced today. The bluestones (some of which are made of dolerite, an igneous rock), were thought for much of the 20th century to have been transported by humans from the Preseli Hills, 250 kilometres (160 mi) away in modern day Pembrokeshire in Wales. A newer theory is that they were brought from glacial deposits much nearer the site, which had been carried down from the northern side of the Preselis to southern England by the Irish Sea Glacier. Other standing stones may well have been small sarsens, used later as lintels. The stones, which weighed about four tons, consisted mostly of spotted Ordovician dolerite but included examples of rhyolite, tuff and volcanic and calcareous ash; in total around 20 different rock types are represented. Each monolith measures around 2 metres (6.6 ft) in height, between 1 m and 1.5 m (3.3-4.9 ft) wide and around 0.8 metres (2.6 ft) thick. What was to become known as the Altar Stone (1), is almost certainly derived from either Carmarthenshire or the Brecon Beacons and may have stood as a single large monolith.

he north eastern entrance was also widened at this time with the result that it precisely matched the direction of the midsummer sunrise and midwinter sunset of the period. This phase of the monument was abandoned unfinished however, the small standing stones were apparently removed and the Q and R holes purposefully backfilled. Even so, the monument appears to have eclipsed the site at Avebury in importance towards the end of this phase.

The Heelstone (5), a Tertiary sandstone, may also have been erected outside the north eastern entrance during this period although it cannot be securely dated and may have been installed at any time in phase 3. At first, a second stone, now no longer visible, joined it. Two, or possibly three, large portal stones were set up just inside the north eastern entrance of which only one, the fallen Slaughter Stone (4), 4.9 metres (16 ft) long, now remains. Other features loosely dated to phase 3 include the four Station Stones (6), two of which stood atop mounds (2 and 3). The mounds are known as 'barrows' although they do not contain burials. The Avenue, (10), a parallel pair of ditches and banks leading 3 kilometres (1.9 mi) to the River Avon was also added. Two ditches similar to Heelstone Ditch circling the Heelstone, which was by then reduced to a single monolith, were later dug around the Station Stones.

Stonehenge 3 II (2600 BC to 2400 BC)

The next major phase of activity saw 30 enormous Oligocene-Miocene sarsen stones (shown grey on the plan) brought to the site. They may have come from a quarry around 40 kilometres (25 mi) north of Stonehenge, on the Marlborough Downs, or they may have been collected from a "litter" of sarsens on the chalk downs, closer to hand. The stones were dressed and fashioned with mortise and tenon joints before 30 were erected as a 33 metres (110 ft) diameter circle of standing stones, with a ring of 30 lintel stones resting on top. The lintels were fitted to one another using another woodworking method, the tongue and groove joint. Each standing stone was around 4.1 metres (13 ft) high, 2.1 metres (6 ft 11 in) wide and weighed around 25 tons. Each had clearly been worked with the final effect in mind; the orthostats widen slightly towards the top in order that their perspective remains constant as they rise up from the ground while the lintel stones curve slightly to continue the circular appearance of the earlier monument. The sides of the stones that face inwards are smoother and more finely worked than the sides that face outwards. The average thickness of these stones is 1.1 metres (3 ft 7 in) and the average distance between them is 1 metre (3 ft 3 in). A total of 74 stones would have been needed to complete the circle and unless some of the sarsens were removed from the site, it would seem that the ring was left incomplete. Of the lintel stones, they are each around 3.2 metres (10 ft), 1 metre (3 ft 3 in) wide and 0.8 metres (2 ft 7 in) thick. The tops of the lintels are 4.9 metres (16 ft) above the ground.

Within this circle stood five trilithons of dressed sarsen stone arranged in a horseshoe shape 13.7 metres (45 ft) across with its open end facing north east. These huge stones, ten uprights and five lintels, weigh up to 50 tons each and were again linked using complex jointing. They are arranged symmetrically; the smallest pair of trilithons were around 6 metres (20 ft) tall, the next pair a little higher and the largest, single trilithon in the south west corner would have been 7.3 metres (24 ft) tall. Only one upright from the Great Trilithon still stands; 6.7 metres (22 ft) is visible and a further 2.4 metres (7 ft 10 in) is below ground.

The images of a 'dagger' and 14 'axe-heads' have been recorded carved on one of the sarsens, known as stone 53. Further axe-head carvings have been seen on the outer faces of stones known as numbers 3, 4, and 5. They are difficult to date but are morphologically similar to later Bronze Age weapons; recent laser scanning work on the carvings supports this interpretation. The pair of trilithons in north east are smallest, measuring around 6 metres (20 ft) in height and the largest is the trilithon in the south west of the horseshoe is almost 7.5 metres (25 ft) tall.

This ambitious phase is radiocarbon dated to between 2600 and 2400 BC. This is slightly before two sets of burials discovered 3 miles (4.8 km) to the west in Amesbury (the Amesbury Archer found in 2002, and the Boscombe Bowmen discovered in 2003) as well as the Stonehenge Archer whose body was discovered in the outer ditch of the monument in 1978.

At a similar time a large timber circle and another avenue were constructed overlooking the River Avon 2 miles away at Durrington Walls. Opposing the solar alignments at Stonehenge, the circle was orientated towards the rising sun on the midwinter solstice, whilst the Avenue led from the river to the circle on an alignment to the setting sun on the summer solstice. Evidence of huge fires on the banks of the Avon between the two avenues also suggests that both circles were linked, and perhaps formed a procession route used on the longest and shortest days of the year. Parker Pearson speculates that the wooden circle at Durrington Walls was the centre of a 'land of the living', whilst the stone circle represented a 'land of the dead'. The Avon would have served as a journey between the two.

Stonehenge 3 III

Later in the Bronze Age, the bluestones appear to have been re-erected for the first time, although the exact details of this period are still unclear. They were placed within the outer sarsen circle and at this time may have been trimmed in some way. A few have timber working-style cuts in them like the sarsens themselves, suggesting they may have been linked with lintels and part of a larger structure during this phase.

Stonehenge 3 IV (2280 BC to 1930 BC)

This phase saw further rearrangement of the bluestones as they were placed in a circle between the two settings of sarsens and in an oval in the very centre. Some archaeologists argue that some of the bluestones in this period were part of a second group brought from Wales. All the stones were well-spaced uprights without any of the linking lintels inferred in Stonehenge 3 III. The Altar Stone may have been moved within the oval and stood vertically. Although this would seem the most impressive phase of work, Stonehenge 3 IV was rather shabbily built compared to its immediate predecessors, as the newly re-installed bluestones were not at all well founded and began to fall over. However, only minor changes were made after this phase. Stonehenge 3 IV dates from 2280 to 1930 BC.

Stonehenge 3 V (2280 BC to 1930 BC)

Soon afterwards, the north eastern section of the Phase 3 IV Bluestone circle was removed, creating a horseshoe-shaped setting termed the Bluestone Horseshoe. This mirrored the shape of the central sarsen Trilithons and dates from 2270 to 1930 BC. This phase is contemporary with the famous Seahenge site in Norfolk.

After the monument (1600 BC on)

The last known construction at Stonehenge was about 1600 BC (see 'Y and Z Holes' below), and the last known usage of it was likely during the Iron Age. Roman coins and medieval artefacts have all been found in or around the monument but it is unknown if the monument was in continuous use throughout prehistory and beyond — or exactly how it would have been used. Notable is the late 7th-6th century BC large arcing Scroll Trench which deepens E-NE towards Heelstone, and the construction of the massive Iron Age hillfort Vespasian's Camp built alongside the Avenue near the Avon. The burial of a decapitated 7th century Saxon man was excavated from Stonehenge. The site was known by scholars during the Middle Ages and since then it has been studied and adopted by numerous different groups.

Function and construction
Main article: Theories about Stonehenge

Stonehenge was produced by a culture with no written language, and at great historical remove from the first cultures that did leave written records. Many aspects of Stonehenge remain subject to debate. This multiplicity of theories, some of them very colourful, is often called the "mystery of Stonehenge."

There is little or no direct evidence for the construction techniques used by the Stonehenge builders. Over the years, various authors have suggested that supernatural or anachronistic methods were used, usually asserting that the stones were impossible to move otherwise. However, conventional techniques using Neolithic technology have been demonstrably effective at moving and placing stones this size. Proposed functions for the site include usage as an astronomical observatory, or as a religious site. Other theories have advanced supernatural or symbolic explanations for the construction.

More recently two major new theories have been proposed. Mike Parker Pearson, head of the Stonehenge Riverside Project, has suggested that Stonehenge was part of a ritual landscape and was joined to Durrington Walls by their corresponding avenues and the River Avon. The area around Durrington Walls henge was a land of the living, whilst Stonehenge was a domain of the dead. A journey along the Avon to reach Stonehenge was part of a ritual passage from life to death, to celebrate past ancestors and the recently deceased. On the other hand, Geoffery Wainwright, president of the Society of Antiquaries of London, and Timothy Darvill of Bournemouth University have suggested that Stonehenge was a place of healing – the primeval equivalent of Lourdes. They argue that this accounts for the high number of burials in the area and for the evidence of trauma deformity in some of the graves. However they do concede that the site was probably multifunctional and used for ancestor worship as well.