Researchers have discovered a major prehistoric stone monument 3km away from the famous Stonehenge standing stones.

The enormous Durrington Walls “superhenge” dwarfs Stonehenge and may have as many as 90 large standing stones associated with it.

Built about 4,500 years ago it has remained hidden for millennia. The use of non-invasive geophysical technologies including ground penetrating radar have begun to reveal the superhenge’s secrets.

Details of the work by the Stonehenge Hidden Landscapes Project were revealed today, on the first day of the British Science Association’s annual festival of science. The festival is hosted this year by the University of Bradford.

Durrington Walls is one of the largest known henge monuments yet discovered. It has a 500m diameter and a 1.5km circumference. Massive effort would have gone into its construction, as it is surrounded by a ditch up to 17.6m wide.

This can be seen, in part, on the ground, but what lies beneath is more surprising. Technology has allowed scientists from the Ludwig Boltzmann Institute for Archaeological Prospection and the University of Bradford to look back through time and see the original monument.

They discovered a row of up to 90 buried standing stones, some of them 4.5m high, taller than a double decker bus.

Many survived because they were pushed over before being buried under the superhenge. Others have disappeared but underground evidence provided by radar and other equipment revealed the pits in which they once stood.

The scientists suggest the stones and henge formed a C-shaped arena. None of the stones have yet been excavated but it is expected they will match the sandstones used to build Stonehenge.

Previous surveys of the surrounding terrain had led scientists to assume only Stonehenge and a smaller henge nearby possessed significant stone structures.

This new survey reveals however that Durrington Walls also had a large row of standing stones. Its dimensions and construction are unique to British archaeology the scientists say.

“This discovery . . . has significant implications for our understanding of Stonehenge,” said Prof Vincent Gaffney of Bradford, who co-leads the project.

The Irish Times will provide daily coverage from the UK festival of science, which continues until Thursday.