Archaeologists say the arrangement of almost 90 large stones was part of a C-shaped arena used for rituals, the largest surviving arena ever discovered.
The arena, thought to have been built during the Neolithic era, would have directly faced the river Avon.
Scientists researching the arena found more than 30 stones completely intact, some of which are up to 4.5 meters tall, with fragments of 60 further stones and foundation pits nearby.
“What we are starting to see is the largest surviving stone monument, preserved underneath a bank, that has ever been discovered in Britain and possibly in Europe,” Bradford University archeologist Vince Gaffney said.
“This is archaeology on steroids.”
Gaffney, who has led the team investigating the ruins, said the site was likely to be a “ritual arena of some sort.” He will present the findings on Monday at the British Science festival in Bradford.
The stones are thought to have been put in place more than 4,500 years ago to form the edge of the arena, which linked up to a natural chalk ridge to complete the circle.
While the scientists have discovered the stones lying down, Gaffney believes they were originally placed upright, but were pushed down when the site was redeveloped into a larger structure known as the ‘superhenge’, Durrington Walls.
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“This is a new element of how the Stonehenge landscape was transformed,” said Gaffney.
Durrington Walls, which spans a full mile in circumference, is one of the world’s largest henge monuments. Historically it would have surrounded smaller enclosures where timber buildings were erected.
Scientists believe the latest stone monument to be discovered was moved about the site as Neolithic builders changed the architecture from the original settings, thought to have been laid in 3,100 BC.
They further believe that a wooden building, found in the chalk, would have been used as a defleshing house before burial ceremonies.
“These latest results have produced tantalizing evidence of what lies beneath the ancient earthworks at Durrington Walls. The presence of what appear to be stones, surrounding the site of one of the largest Neolithic settlements in Europe, adds a whole new chapter to the Stonehenge story,” National Trust archaeologist for the Avebury and Stonehenge world heritage site Nick Snashall said.