London, England (CNN) -- Archaeologists studying the iconic Stonehenge monument in southern England have uncovered a second prehistoric henge-like circle only 900 meters away, which they hope will shed more light on the mysterious stone landmark.
The remains, comprising a circular ditch surrounding a ring of 24 internal pits up to one meter in diameter and designed to allow posts to support a free-standing, timber structure up to three meters high -- are thought to date from the late Neolithic period, some 4,500 years ago.
"Although it would have been made out of timber rather than stone, it's comparable in scale to the existing Stonehenge monument," said Henry Chapman of the University of Birmingham in central England.
Chapman was one of the British-led team involved in a multi-million dollar project to "map" the World Heritage site, using state-of-the-art imaging technology to recreate "virtually" the iconic monument and its surroundings.
The images, which resemble a lunar landscape, provide an outline of the circle buried under the surface with its opposing north-east and south-west entrances, together with what archaeologists believe to be a burial mound in the center.
"Rather than giving us a map or plan of what is buried, this technology allows us to see it in three dimensions," Chapman told CNN. "We can almost excavate the site virtually by peeling off five centimeters at a time to see what is there."
Project leader, Professor Vince Gaffney of the University of Birmingham, hailed the find as one of the most significant yet for those researching Britain's most important prehistoric structure.
"This finding is remarkable," he said in a statement on the university's website. "It will completely change the way we think about the landscape around Stonehenge.
"People have tended to think that as Stonehenge reached its peak it was the paramount monument, existing in splendid isolation. This discovery is completely new and extremely important in how we understand Stonehenge and its landscape."
Chapman added that the find may be the start of an exciting new chapter at Stonehenge. "We're just in the first year of a four-year project, so we'd expect to find lots more between the known monuments we see at present and hopefully fill the gaps in our knowledge," he said.
Debate has raged about the origins and purpose of Stonehenge, located on Salisbury Plain approximately 90 miles west of London.
Known for its orientation in relation to the rising and setting sun, the circle of stones represented a prehistoric temple to some. Others argued it was an astronomical observatory. Or that it was a marker of time.
But last year, archaeologists unearthed a new stone circle a mile from Stonehenge that they said lent credence to the theory that the famous monument was part of a funeral complex.
Dubbed "Bluestonehenge" after the color of the 25 Welsh stones of which it was once composed, the new find sat along the banks of the nearby River Avon.
University of Bristol archaeologist Joshua Pollard suggested Neolithic peoples would have come down river by boat and literally stepped off into Bluestonehenge. They may have congregated at certain times of the year, including the winter solstice, and carried remains of the dead from Bluestonehenge down an almost two-mile funeral processional route to a cemetery at Stonehenge to bury them.
The latest project, which is supported by the site's landowner, the National Trust, and facilitated by English Heritage, brought together the most sophisticated geophysics team ever to be engaged in a single archaeological project in Britain, involving archaeologists and other specialists from the UK, Austria, Germany, Norway and Sweden.