We've all heard of Stonehenge, even if most of us aren't quite sure what a henge is. But it turns out that the mysterious ancient monument may have been dwarfed by a nearby contemporary. Scientists working with the Stonehenge Hidden Landscape Project have discovered evidence of a massive henge just two miles away. Here's a visual reconstruction for scale:

“We don’t think there’s anything quite like this anywhere else in the world,” Vince Gaffney of the University of Bradford, one of the project's lead researchers, said at the British Science Festival on Monday. “This is completely new and the scale is extraordinary.”

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The 100-odd stones, which were discovered using ground-penetrating radar technology, sit beneath three feet of earth and are thought to be 4,500 years old -- roughly the same age as the more famous henge down the road. The new find sits beneath a henge known as Durrington Walls, a previously discovered, younger "superhenge" thought to once be one of the largest settlements in Europe, spanning a space five times larger than Stonehenge.

While some of the stones are only known by the depressions they left behind, others are still buried. The researchers believe the stones may have been deliberately toppled over at the time that Durrington Walls was constructed. Some of the stones are as tall as 15 feet.

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Scientists still aren't exactly sure what purpose Stonehenge served. Was it a sacred space, for rituals and religious celebrations? Was it some kind of astronomical calendar? An elite burial ground? As the structures grow more and more common, our theories may have to change.

"Everything written previously about the Stonehenge landscape and the ancient monuments within it will need to be rewritten," Paul Garwood, an archaeologist and lead historian on the project at the University of Birmingham, told CNN.

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