LONDON, June 29 (Xinhua) -- The world famous Avebury stone circle, considered as one of the greatest marvels of prehistoric Britain, also contains a square, research released Thursday revealed.
Archaeologists have found a striking and apparently unique square monument beneath the Avebury stone circle, a UNESCO World Heritage site cared for by the National Trust, in Wiltshire.
The research team, led by the Universities of Leicester and Southampton, performed a soil resistance survey and used ground-penetrating radar to investigate the stone circle.
Excavations were originally started in 1939 by the archaeologist Alexander Keiller. That work pointed to the existence of a curious angular setting of small standing stones close to a huge upright one known as the Obelisk. But Keiller's research was interrupted by the outbreak of the World War II.
Nick Snashall, National Trust archaeologist at Avebury, said: "This discovery has been almost 80 years in the making, but it's been well worth waiting for."
Joshua Pollard from the University of Southampton said: "Our careful program of geophysical survey has finally completed the work begun by Keiller. It has shown the line of stones he identified was one side of a square of megaliths about 30 meters across and enclosing the Obelisk."
"Megalithic circles are well known from the time when Avebury was built during the late Neolithic (3rd millennium BC), but square megalithic settings of this scale and complexity are unheard of."
The site contains three stone circles, one of them the largest stone circle in Europe measuring 330 meters across and originally comprised around 100 huge standing stones, built as a sacred meeting place and possibly aligned to the stars.
Mark Gillings, academic director and reader in archaeology at the School of Archaeology and Ancient History at the University of Leicester, said: "We have detected and mapped a series of prehistoric standing stones that were subsequently hidden and buried, along with the positions of others likely destroyed during the 17th and 18th centuries."
"Together, these reveal a striking and apparently unique square megalithic monument within the Avebury circles that has the potential to be one of the very earliest structures on this remarkable site."
A spokesman for the National Trust said: "The discovery of new megaliths inside the monument was a great surprise, pointing to the need for further archaeological investigations of this kind at the site."
"If proved correct, it may help understand the beginnings of the remarkable Avebury monument complex, and help explain why it was built where it was," said the National Trust spokesman.