Stonehenge is one of the most prominent prehistoric monuments in Britain. The Stonehenge seen today is the final phase that was completed about 3,500 years ago.
According to the website of the monument, Stonehenge was built in four phases:
First phase: The first version of Stonehenge was a large earthwork or a Henge, consisting of a ditch, a bank and the Aubrey holes, probably built around 3100 BC.
The Aubrey holes are round pits in the chalk, about a meter (3.3 feet) wide and deep, with steep sides and flat bottoms.
They form a circle with a diameter of about 86.6 meters (284 feet).
Excavations revealed cremated human bones in some of the lime padding, but the holes themselves were probably not made to be used as graves, but as part of a religious ceremony.
After this first phase, Stonehenge was abandoned and remained untouched for more than 1,000 years.
Second stage: The second and most dramatic phase of Stonehenge began around 2150 BC, when about 82 bluestones from the Preseli Mountains in southwest Wales were transported to the site. It is thought that the stones, some of which weigh 4 tons each, were towed to the waters on rollers and sleds at Milford Haven, where they were loaded on rafts.
They were carried on the water along the south coast of Wales and the rivers Avon and Frome, before they were towed over land in the vicinity of Warminster and Wiltshire.
The last stage of the journey was mainly through water, over the Wylye River to Salisbury, then the Salisbury Avon to the west of Amesbury.
The journey covered almost 240 miles, and once at the location the stones were placed in the middle to form an incomplete double circle.
In the same period the original entrance was widened and a few Heel Stones were established. The nearest part of the Avenue, which connects Stonehenge with the river Avon, was built in line with the midsummer rise.
Third phase: The third phase of Stonehenge, which took place about 2,000 years before Christ, saw the arrival of the sarsstones (a kind of sandstone), which were larger than the bluestones.
They were probably brought from the Marlborough Downs (40 kilometers or 25 miles north of Stonehenge).
The largest of the sarsen stones transported to Stonehenge weighs 50 tons, and transport over water would not have been possible, so there is a suspicion that they have been transported with sleds and ropes.
Calculations have shown that 500 men with leather cables would have been pulled to draw one stone, with another 100 men needed to lay the rolls for the sled.
These stones were arranged in an outer circle with a continuous piece of lintel – horizontal supports.
Within the circle, five trilite structures consisting of two standing stones and a third over the top as a lintel – were placed in a horseshoe shape, which is still visible.
Last stage: The fourth and final phase took place just after 1500 years BC, when the smaller bluestones were rearranged in the horseshoe and the circle that can be seen today.
The original number of stones in the bluestone circle was probably around 60, but these have since been removed or broken. Some remain as stumps below ground level.