2. On the summer solstice, happy druids and Lord of the Rings fans can now mill freely - but quietly and soberly - among the ancient stones unfettered by nasty plastic fences, thanks to English Heritage.

3. The monument, near Amesbury in Wiltshire, is made up of a 100ft wide outer circle of bus-sized Sarsen stones, surrounding an inner horseshoe of bluestones from the Preseli mountains in south-west Wales. Inside that lies another horseshoe of giant archways.

4. Stonehenge began as a circle of timbers surrounded by a ditch, over 5,000 years ago. The bluestones were added in around 2100BC, their transportation by ancient man from a mountain range 245 miles away posing one of the greatest mysteries of the monument. About 200 years later the outer ring was added.

5. All this sweat and toil on the part of our neolithic forebears begs the question - why? Some think the stones' position means that Stonehenge was used as some kind of astral calculator - on midsummer's dawn, the sun rises in a direct line with the monument's huge heel stone.

6. But others believe that Stonehenge was merely a religious temple, housing pagan rituals and ceremonies. The Druids, the high priests of the Celts, may have used the central altar stone - as immortalised by Thomas Hardy - for animal or even human sacrifice.

7. But they certainly didn't build it, despite what 17th century Stonehenge antiquary John Aubrey thought. Carbon dating shows that Stonehenge was finished about 1,000 years before the Celts moved in.

8. Several less scientific theorists propose instead that Stonehenge was built by Merlin, the devil or aliens.

9. And that it is a landing site for UFOs, because of the crop circles that frequently appear around it. (Although in the pubs around the crop circles, there frequently appear mischievous hay-covered crusties with sore feet.)