Each year, hundreds of visitors to London hop on coach tours to Stonehenge with little more than a vague idea of what to expect.

The attraction is famous the world over and many different theories have been put forward to explain its significance.

However, with the first work on the site dating back to about 3,000 BC, visitors can be sure that they are seeing something special.

According to English Heritage, it is believed that the initial Stonehenge monument consisted of a circular ditch and bank about 100m in diameter, which may have featured a ring of 56 wooden posts.

Approximately half a century later, workers carried the first stones some 150 miles from the Preseli Hills in Pembrokeshire.

These bluestones were erected in an arc but later dismantled and replaced by another arrangement, which included the larger sarsen stones from Marlborough Downs.

These were erected into a horseshoe shape enclosed in a circle, with the open end of the inner arrangement facing the midsummer sunrise.

Many of these stones and evidence of numerous other arrangements can be seen today on tours to Stonehenge, which is located about 85 miles to the west of London.