Stonehenge is renowned the world over and, together with surrounding prehistoric monuments, is a World Heritage Site. It was begun in the Neolithic period, about 3000 BC as a circular ditch surrounding stone or wooden posts. The stones arrived about 500 years later, some (the Sarsen stones) from the Marlborough Downs about 16 miles to the north, other (the bluestones) from the Preseli Hills some 150 miles to the west, in Pembrokeshire. No one knows for certain why it was built - there is no shortage of theories. But it would have taken not only a lot of effort, but also a lot of organisation, to build Stonehenge. Further, it is situated in a landscape packed full of other monuments and reminders of our prehistoric ancestors. Stonehenge is extremely popular. There is a busy visitor centre with a compelling museum, exhibition gallery and reconstructed round-houses. You are transported part-way to the circle by shuttle bus, after which you can walk. The area has been landscaped so that the visitor centre is not visible from the monument. Note: Many visitors are disappointed by how crowded Stonehenge can be - and also that the circle is smaller than they have imagined.