What Lies Beneath Stonehenge?

A new Smithsonian Channel show reveals groundbreaking research that may explain what really went on there

(Photo by Henrik Knudsen, with thanks to English Heritage)
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The Stonehenge Hidden Landscapes Project is different from everything that came before it. When Gaffney and his team started their work, they were less interested in theories than in data. To that end, they concentrated on taking what amounts to a three-dimensional and yards-deep photograph of the entire landscape. “The perceived wisdom was driven by the monuments we knew about,” says Gaffney. “We’ve put in the data between the monuments.”


Chris Gaffney, Vince’s younger, slighter and less voluble brother, was one of the instigators of this new approach. The duo’s grandfather was a metalwork teacher from Newcastle with an interest in archaeology, who took his clever grandchildren on trips to Hadrian’s Wall, the old barrier between the Roman Empire and the blasted north. Small wonder that Vince became an archaeologist and Chris a geophysicist, now at the University of Bradford.

The Gaffney brothers’ interest in new technologies that were becoming available to archaeologists led them to the first GPS-guided magnetometer systems. A magnetometer has sensors that allow a geophysicist to see evidence of historic building, and even ancient ditch-digging, beneath the soil by mapping variations in the earth’s magnetic field. The GPS-guided versions were able to pinpoint some of those discoveries to within one centimeter. The Gaffneys believed that Stonehenge scholarship needed a massive magnetometer- and radar-led survey of the whole site. “We just didn’t know if anything’s there,” Vince Gaffney recalled. “So we’re constructing various hypotheses on the basis of something we don’t know.”

Around the same time, an Austrian archaeologist named Wolfgang Neubauer, now of the Boltzmann Institute, was hoping to conduct large-scale projects all over Europe using tools including GPS magnetometers and ground-penetrating radar. Neubauer’s team had also developed software to process the 40 or 50 gigabytes of raw data that these instruments could create in a day. Suddenly, instead of waiting weeks or months to see what the machines had found, it was possible to cover several acres with magnetometers and radar in a day and to display that information on a screen almost instantaneously.

One of the areas Neubauer wanted to scan was Stonehenge, and in the spring of 2009 he contacted Vince Gaffney. A few months later, the Boltzmann Institute and the University of Birmingham—plus several other British and European universities, museums and companies that contributed expertise and resources—began their collaboration at Stonehenge.

Their first days on site, Gaffney recalled, were “like a geophysical circus has come to town.” Tractors pushed the ground-penetrating radars, which looked like high-powered lawn mowers. All-terrain vehicles dragged the magnetometer sensors on long strings. Delicate instruments covering hard, uneven ground kept mechanics and technicians busy. “I have seen one of our magnetometers shear clear apart in front of me,” said Gaffney. “It was back in service the next day.” In all, the fieldwork took about 120 days, spread over four years.


In a multimedia room at the University of Birmingham there was a vast touch screen, six feet by nine, on which a new map of the Stonehenge landscape appeared. Gaffney pointed out the key features.

There was Stonehenge itself, marked by the familiar circles. To the north was the long, thin strip called the Stonehenge Cursus or the Greater Cursus, which was demarcated by ditches, and ran east to west for nearly two miles. (The Cursus was given its name by the antiquarian William Stukeley in the 18th century because it looked like an ancient Roman race course. Its construction predates the first building work at Stonehenge by several hundred years.) Gaffney also pointed out the Cursus Barrows—hillocks containing mass human graves—just south of the Cursus itself, and King Barrow Ridge to the east.

Scattered all over the map were blotches of black: features without names. These were new finds, including the more than 15 possible new or poorly understood Neolithic monuments. Gaffney emphasized possible, acknowledging that it will require digging—“the testimony of the spade”—to discover precisely what was there.

Standing in front of this constellation of evidence, he seemed unable to decide where to start, like a child at the Christmas tree. “These are little henge monuments,” he said, touching the screen to highlight a group of black smudges. “Nice little entrance there, and a ditch. These things we know nothing about.”

He saved his greatest enthusiasm for the discoveries that had been made in the Cursus. This feature, said Gaffney, had always been thought of as a “bloody great barrier to the north of Stonehenge.” Nobody knew quite what it was for. Because the Cursus runs east to west, archaeologists have always believed that its presence owes something to the passage of the sun. The monument must be significant: It was dug in the fourth millennium B.C. using antler picks—hundreds of thousands of man-hours went into its construction.

The Hidden Landscapes Project’s instruments discovered several new clues. First of all, they found gaps in the ditch, in particular a very large break in the northern side, to allow people to enter and exit the Cursus. Now, instead of seeing the Cursus exclusively as a monument that encouraged movement along the path of the sun, east to west, Gaffney began to consider these gaps as “channels through the landscape” to guide the movement of people north to south.

A bigger discovery, Gaffney says, was a “bloody huge” pit about five yards in diameter at the eastern end of the Cursus. Today it lies buried at least three feet below the surface of the ground. Such a pit was much too large for a practical use—for instance, burying trash—because of the labor involved in digging it. In the archaeologists’ minds it could only have ritual implications, as “a marker of some kind,” Gaffney said. What’s more, if you drew a straight line between the pit and the heelstone at Stonehenge, it ran directly along the final section of the Avenue, on the path of the sunrise on the summer solstice.

“We thought, That’s a bit of a coincidence!” Gaffney recalled. “That was the point at which we thought, What’s at the other end? And there’s another pit! Two pits, marking the midsummer sunrise and the midsummer solstice, set within a monument that’s meant to be something to do with the passage of the sun.”

With his hands passing over the map, Gaffney showed how—on the longest days of the year—the pits formed a triangle with Stonehenge marking sunrise and sunset.

About Ed Caesar

Ed Caesar is a British author and feature writer who contributes to the New York Times Magazine, the Atlantic, Outside, the Sunday Times Magazine of London and British GQ. Caesar was named Writer of the Year in 2013 by the U.K.'s Professional Publishers Association.

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