Hidden remains of an extraordinary neolithic monument that could be unique in the world have been found buried beneath the ground a mile from Stonehenge.
More than 4,500 years ago, at least 90 huge stone monoliths lined an impressive "arena" that may have been used for religious rites or solstice rituals.
Now lying on their sides covered by three feet of earth, they remainedundiscovered until archaeologists equipped with ground-penetrating radar probed the area around the famous stone circle on Salisbury Plain.
They are the most important find to emerge so far from the Hidden Landscapes project which is using state-of-the-art technology to map "invisible" archaeological features embedded in the Wiltshire countryside.<
The stones, some measuring nearly 15ft, were placed along the south-eastern edge of what later became the Durrington Walls "superhenge" - a circular enclosure ringed by a ditch and bank that at nearly a mile across is the largest earthwork of its kind in the UK.
Experts believe the stones, which may have been imbued with magical properties, were not originally part of the henge but were deliberately toppled before being incorporated into it.
Ninety stones have been discovered so far, and there may be more.What kind of material they are made of is unknown, but they could be similar to the giant sandstone "sarsens" of Stonehenge.
Prof Gaffney believes the stones may have been planted by the same people who built Stonehenge, but is sceptical about a direct link between the two monuments.
They were placed along a steep slope, or scarp, cut into a natural dry valleyto form a C-shaped feature.
Precisely why the stones were put there remains a mystery. Part of Durrington Walls is aligned with the rising sun on the winter solstice, the shortest day of the year, which may be significant.
The archaeologists believe that at some stage the stones were pushed over and incorporated into the emerging henge. This was not an act of vandalism but a deliberate attempt to preserve whatever it was about the stones that seemed so important.