June 22 (UPI) -- Archaeologists have discovered the markings of a prehistoric structure surrounding Durrington Walls, an ancient monument positioned just 1.9 miles northeast of Stonehenge.
The discovery suggests that roughly 4,500 years ago, Neolithic builders -- the same people who constructed Stonehenge -- dug a series of deep shafts, forming a circle spanning 1.2 miles in diameter, according to a study published Sunday in the journal Internet Archaeology.
Until recently, the pits -- usually discovered a few at a time -- were thought to be sinkholes or dew ponds. But their uniformity inspired further investigation, and aerial surveys using a combination of technologies, including ground-penetrating radar and magnetometry, revealed a larger pattern.
"The area around Stonehenge is among the most studied archaeological landscapes on earth and it is remarkable that the application of new technology can still lead to the discovery of such a massive prehistoric structure which, currently, is significantly larger than any comparative prehistoric monument that we know of, in Britain at least," Vincent Gaffney, one of leading archaeologists on the survey effort, said in a news release.
Because the Durrington Walls, one of Britain's largest monument sites, sits at the center of the massive circle of shafts, researchers suspect the pits served as a boundary to lands considered sacred by the population.
"As the place where the builders of Stonehenge lived and feasted, Durrington Walls is key to unlocking the story of the wider Stonehenge landscape, and this astonishing discovery offers us new insights into the lives and beliefs of our Neolithic ancestors," said Nick Snashall, National Trust archaeologist for the Stonehenge and Avebury World Heritage Site. "The Hidden Landscapes team has combined cutting-edge, archaeological fieldwork with good old-fashioned detective work to reveal this extraordinary discovery and write a whole new chapter in the story of the Stonehenge landscape."
While Stonehenge is positioned in relation to the summer and winter solstices, marking the limits of the sun's range, the newly discovered pits suggest ancient recognition of even larger cosmological phenomena.
It's not clear whether the pits were intended to guide people toward the ancient monuments or keep people out, but the shafts suggest the region's monuments were part of an expansive cultural and spiritual tradition.
"Seemingly isolated features have been shown to be linked and significant to the story of the emergence of the ritual landscape," said Chris Gaffney, archaeological geophysicist at Bradford University. "An interdisciplinary approach, using a battery of techniques, has been key to the successful understanding of this complex but structured element of the landscape around Durrington Walls."
In addition to the Durrington Walls, the boundary formed by the pits also includes a second monument, the Larkhill causewayed enclosure, built 1,500 years before Stonehenge.
The latest discovery suggests Britain's Stone Age populations were remarkably sophisticated and capable of tremendous geoengineering feats. Researchers say digging such massive pits with primitive tools is every bit as impressive as arranging giant stones.
"Seeing what is unseen! Yet again, the use of a multidisciplinary effort with remote sensing and careful sampling is giving us an insight to the past that shows an even more complex society that we could ever imagine," said Richard Bates, an earth scientist at the University of St. Andrews.
"Clearly sophisticated practices demonstrate that the people were so in tune with natural events to an extent that we can barely conceive in the modern world we live in today," Bates said.