LONDON -- Archeologists said Monday that they have discovered a major prehistoric monument under the earth near Stonehenge that could shed new light on the origins of the mystical stone circle in southwestern England.

Experts from a group of British universities led by the University of Bradford say the site consists of at least 20 huge shafts, more than 10 metres (32 feet) in diameter and 5 metres (16 feet) deep, forming a circle more than 2 kilometres (1.2 miles) in diameter.

The new find is at Durrington Walls, the site of a Neolithic village about 2 kilometres (1.2 miles) from Stonehenge,

Researchers say the shafts appear to have been dug around 4,500 years ago, and could mark the boundary of a sacred area or precinct around a circular monument known as the Durrington Walls henge.

Richard Bates, of the University of St. Andrews School of Earth and Environmental Sciences, said the findings -- made with remote sensing and sampling - provided “an insight to the past that shows an even more complex society than we could ever imagine.â€

University of Bradford archeeologist Vince Gaffney said it was “remarkable†that Stonehenge, one of the most studied archeological landscapes in the world, could yield such a major new discovery.

“When these pits were first noted it was thought they might be natural features - solution hollows in the chalk,†he said. But geophysical surveys allowed scientists to “join the dots and see there was a pattern on a massive scale.â€

Britain is dotted with stone circles build thousands of years ago for reasons that remain mysterious.

The most famous is Stonehenge, a huge monument built between 3000 B.C. and 1600 B.C. that is one of Britain's most popular tourist attractions.

It's also a spiritual home for thousands of druids and mystics who visit at the summer and winter solstices -- though this weekend's summer solstice celebrations were scuttled by a ban on mass gatherings because of the coronavirus pandemic.