Stonehenge - visiting from London
The stone circle at Stonehenge is approximately 2.5 hours from London and a popular day-trip for 
many visitors . This is a brief look at its history and theories about why it's there. It's one of the UK's premier monuments, but has come under sustained criticism for the way it's portrayed and presented to the public. The plans to divert the nearby main road (A303) away from the site, were shelved after costs escalated dramatically to £450m.
There is a related article about the henge at Avebury which is nearby and although I would never discourage visitors from seeing Stonehenge, there is something unseemly about the way the experience is delivered. For me personally, Avebury is more unusual, older, it's free, and you can touch it. If you make the trek out to Stonehenge, try and fit Avebury in too - it's one of the most spectacular monuments in the UK.
Phases of Stonehenge
The first phase of Stonehenge was a large earthwork or 'henge', comprising a ditch, bank, and the "Aubrey holes", all probably built around 3000 BC. It's not known what the holes are for, but shortly after construction it was abandoned for over 1,000 years
The second phase started around 2150 BC. Eighty two bluestones from the Preseli Mountains, in Wales were transported to the site. A journey of over 200 miles, it involved their removal to the river, raft construction and floating, the navigation of many rivers, then finally - the dragging of the bluestones to the site. Logistically complex now, the planning and effort required at the time is scarcely imaginable.
The third phase of Stonehenge, started around 2000 BC, and involved the transport and erection of the great Sarsen stones from the Marlborough Downs; around 25 miles away. Weighing up to 40 tons, they could only have been transported across land and estimates suggest that each stone would require a 'team' of 500 hauling, and at least 100 moving the rollers.
These Sarsen stones had lintels placed on top and were formed into a circle. Inside the circle are the five Trilithons, in a horseshoe arrangement. These have remained unchanged until the present day.
The fourth phase started around 1500 BC and involved the bluestones being re-arranged into a horseshoe. They have remained in that configuration; though the stones have gone, leaving only the stumps to be seen at ground level.
Why was Stonehenge built?
The latest theory (2008) tends to dismiss the idea that Stonehenge was a holy place, or a place for calculating calendar dates - but suggests Stonehenge was a site of healing. Unwell or injured people made a pilgrimage to the site, in the desperate hope of getting better.
The theory focuses on the bluestones which were transported from South Wales. The likely explanation for such a long and arduous journey was their original proximity to healing springs found in the Preseli Mountains. This is backed up by many skeletons found on the site, which have an unnatural concentration of skeletal trauma. The possibility of relief from tremendous pain and suffering is a great motivator for people travelling distances and also to go to such exceptional lengths to transport the stones themselves.
This has not been met with approval by the 'Stonehenge as a calendar' group. Also, a convincing 
argument where the potency of the earth was being determined, so that crops would not fail. Again, a critical aspect of early life in Britain. Having enough food was essential in order for any kind of civilised society to operate.
The religious view that the site was a place where druids worshipped is still powerfully supported, though undermined by Stonehenge pre-dating the existence of druids, by more than 1,000 years.
Getting to Stonehenge
The best way of reaching Stonehenge from London based transport is either: take the train to Salisbury and catch the Stonehenge bus from there (approximately 2.5 hours), or take a coach tour to the site direct, from London. Many vendors offer this service, so check prices on the Internet before making a selection.
Excerpt from a programme about Neolithic monuments in the UK including Stonehenge, Woodbury and Avebury.
Stonehenge is a UNESCO World Heritage Site and there is an entry fee to see the stones. You are not permitted to enter the circle itself, just to skirt around it.
