An archeological dig at a "super-henge" site near Stonehenge where researchers said they had detected a "major new prehistoric stone monument" last year has found no giant stones after all.

"What  we thought was a ring of stones here was actually a ring of massive, massive posts," Vince Gaffney, British project leader for the Stonehenge Hidden Landscape Project, told CBC News following the dig earlier this month.

He said he was surprised by the discovery, but not disappointed.

"What we've done is discover an entirely new monumental phase," he said. "No one has ever seen this before."

Stonehenge and Durrington Walls

The buried monument was detected at Durrington Walls, the location of a huge, circular henge bank about 480 metres in diameter. (Stonehenge Hidden Landscapes Project)

Last September, the Hidden Landscape Project announced an astonishing discovery at Durrington Walls, about  three kilometres northeast of Stonehenge. Based on remote sensing using ground-penetrating radar, the team announced it believed that a row of up to 90 standing stones, each up to 4.5-metres high, had been buried one-metre deep beneath the three-metre high bank of a "super-henge" about 480 metres in diameter.

While Stonehenge is known for its circle of giant stones, Gaffney said most henges are ring-shaped prehistoric monuments consisting of a raised bank of earth with a ditch behind it, like the one at Durrington Walls and a circular bank 100 metres in diameter that surrounds the stones of Stonehenge itself.

Detecting another monument — an apparently huge one — buried under the Durrington Walls henge bank was a surprise and considered a significant find.

But Mike Parker-Pearson at University College London, leader of another archeological project in the Stonehenge area, later suggested that the radar signals might not represent huge stones at all.

Parker-Pearson's Stonehenge Riverside Project had been excavating in the area for years, and had found some very large pits that had once contained wooden posts. The pits were later filled in with rubbish and capped with chalk — a mineral that could look like stone when viewed with ground-penetrating radar.

So what was really buried under the bank at Durrington Walls? The only way to find out was to dig.

Durrington Walls dig

During a dig at Durrington Walls earlier in August, archeologists uncovered pits about 1.5 metres deep that once held huge wooden posts up to 60 centimetres wide and five metres tall. (Abby George/National Trust)

In early August, the teams run by Gaffney and Parker-Pearson collaborated with the National Trust, a charity that preserves special lands, buildings and ancient monuments in the U.K., to excavate at two of the "standing stone" signals detected last year.

"The geophysics can show you there's something there, but it can't necessarily tell you what," said Nick Snashall, an archeologist with the National Trust who participated in the dig.

What the researchers found was massive pits about 1.5 metres deep that once held huge wooden posts up to 60 centimetres wide and five metres tall. They also found ramps about three metres long that would have been used to slide the posts into the pits.

Built and rebuilt

The ancient builders would not have had metal tools — they would have done all that digging with picks made from deer antlers, Snashall said. And there were no trees nearby, so all the posts would have been brought from a considerable distance.

"So it's an enormous amount of effort," she said.

The researchers suspect that there were once hundreds of timber posts erected around the half-kilometre-wide circle. While other circles of timber posts have been found at temple sites near Stonehenge, most are much smaller — perhaps 30 metres in diameter.


While other circles of timber posts such as Woodhenge have been found at sites near Stonehenge, most are much smaller than the henge at Durrington Walls. (GothamNurse/Flickr, CC BY-SA 2.0)

But despite the scale of the timber circle at Durrington Walls, it didn't last long.

Marks around the pits show that the posts were removed a short time later by lifting and twisting them out. Then the pits were filled with chalk and buried when the henge bank and ditch were constructed a few years or decades later, no later than 2450 BC.

The evidence that the Durrington Walls monument was built and then rebuilt in a completely different way shortly after Stonehenge's construction suggests that this was a dynamic time characterized by a "changing of minds" and perhaps a shift in power, Snashall said.

"It really is quite sort of an exciting and dynamic part of the story of our ancient ancestors."

Antler pick

The ancient builders would not have had metal tools, so they would have done all that digging with picks made from deer antlers, found during the August dig. (National Trust)

And while a short-lived monument built with timber posts may not capture the imagination like giant stones that have stood for thousands of years, the researchers say the newly discovered monument is still huge and surprising, given that the Stonehenge landscape has been studied and excavated for hundreds of years.

"Still there are huge new monuments that we knew nothing about," Snashall said. "There's still a huge amount out there that I think we still don't know about."