Broken antler pickaxes in the ditch date its construction to about 2470 BC to 2280 BC. At least one entrance has been discovered, on the east side, and it contained a specially placed deposit of antlers, an antler pickaxe, cattle bones and stone and flint tools.
The team also found the riverside end of the avenue to Stonehenge. It was marked by two parallel ditches about 54 feet apart. These originally held posts, forming a small palisade on either side. The avenue apparently terminated at or close to the outer bank of the newly discovered henge.
Archaeologist Josh Pollard of Bristol University, a co-director of the project, noted that the circle "should be considered an integral part of Stonehenge rather than a separate monument, and it offers tremendous insight into the history of its famous neighbor."
Previous research had shown that Stonehenge originally consisted of 56 bluestones set in a circle inside a ditch and bank. Sometime about 2500 BC, those stones were moved to their current location, leaving behind the holes now known as Aubrey holes.
But there are 80 bluestones in Stonehenge and only 56 Aubrey holes, Parker Pearson said.
"Where did the other 24 stones come from? I think we have solved that problem. They uprooted the other circle and moved the stones. Why they did it, we don't know."
But "what it tells us for sure is that the river is essential to understanding Stonehenge," Parker Pearson added, because why else would the ancient builders have erected a monument there?
Burning ceremonies appear to have been important rites at the site as well. When the stones at Bluestonehenge were pulled out, a lot of topsoil fell in, and that topsoil, the team found, is full of charcoal.
"They were building a lot of fires there. That may have been where they were cremating bodies" before burying them at Stonehenge, Parker Pearson said.
"This is a very exciting time," he added. "Our seven years of work have completely rewritten the story of Stonehenge."
But the work is not done. For example, Parker Pearson said the team thinks it has located the quarry where the sarsen stones were excavated and is now working to confirm the identification.
It is also using isotopic analysis of teeth from cattle that were eaten during the large celebrations at the site and during its construction to determine where the animals came from.
"The vast majority are coming from long distances away," many of them from Wales or southwest England, he said. "There was a very large [number] of animals being brought to support the population building Stonehenge."
The discovery was announced Monday by the National Geographic Society, which funded much of the research.
Full details will be published in February, Parker Pearson said.