​Uncovering the long-hidden secrets of Stonehenge

Studying the mysteries of Stonehenge 06:44

With Mark Phillips this morning we'll take a walk among the Stonehenge stones:

At Stonehenge, it's always been about the Sun. For more than 4,000 years, the monument has stood like a giant sundial, marking the longest day of the year, and the shortest -- taking aim at the Sun like a giant stone gunsight.

Yet, Stonehenge is also about mystery. The big stone circle is only the most obvious part of the site. Lesser monuments -- some much older, and most of them buried under the soil now -- stretch for miles across the landscape.

And they're being looked at in a way that's never been possible before, using high definition, ground-penetrating radar and other magnetic- and resistance-sensitive survey equipment in what's being called the Hidden Landscapes Project.

A documentary team from the Smithsonian Channel has been following the archaeologists around; and -- using computer generated imagery -- it's been digitally reconstructing some of the monuments that have long since disappeared, like a burial chamber built of wooden posts, with timbered walls and covered with earth. It predates Stonehenge by centuries, and would have held the remains of around 50 bodies.

Henry Chapman, an archaeologist from the University of Birmingham, England, says the project has produced more data than they know what to do with.

"It's sort of the sweet shop problem," Chapman said. "That's when you're presented with loads of information, [so you] think, 'I want some more now!'"

The new data has helped answer some old questions, like whether the giant stone circle -- now somewhat gap-toothed -- was ever complete. The digital probing and some dry patches that emerged during a recent drought seem to show that Stonehenge was once, in fact, a full circle.

Mark Bowden, of English Heritage, said the data revealed a series of parch marks, "which showed us the positions of some stones which we'd never seen before at Stonehenge."

Chapman said, "In many ways, I think we've had almost a false understanding of Stonehenge . . . because we haven't been able to see the whole picture."

The new imagery shows what they call the Greater Cursus, running like a huge ditch and mound in a massive loop across the countryside. Archeologists had known it was there, but were never sure what it contained or what it was for.