Stonehenge

Stonehenge is one of the greatest unexplained mysteries of the world. It's certainly no hoax (estimated to be more than 5,000 years old) and is probably the most important prehistoric monument in the whole of Britain.

When you visit Stonehenge, you'll find yourself driving for miles through rolling hills and countryside until, suddenly, you catch sight of this bizarre structure. There's an eerie feel to the area around Stonehenge, and for thousands of years it has soon silently, giving away few clues as to the meaning of its existence.
Excavations have revealed that Stonehenge was built in four stages:

1. First a series of holes were dug around 3,100 BC for religious ceremony. 
2. Then, more than 1,000 years later, the most dramatic stage of building took place. Huge bluestones from mountains in Wales were lugged more than 240 miles to the Stonehenge site. Why would anyone do this in the age before the wheel? And how would they accomplish such a feat? These are true unexplained mysteries - because it really wouldn't have been hard to find rocks closer nearby. The stones were then set up to form an incomplete double circle, aligned perfectly with the midsummer sunrise. 
3. The third stage in 2,000 BC saw the arrival of the more stones, transported by land from the Marlborough Downs some 25 miles away.
4.  Finally, after a further 500 years had passed, someone felt the need to rearrange the massive Welsh bluestones into the familiar horseshoe and circle we see today.

One of the great unexplained mysteries of ancient man, the meaning of Stonehenge is still not clear today. Was it a temple, a burial ground, an observatory, or an ancient calendar?