The idea suggests prehistoric people built a ring of stone circles in modern-day Dartmoor National Park around the same time that Stonehenge was created—and the new finds have just added another piece to the puzzle

The “sacred arc” theory might sound like a plot point straight out of a fantasy novel, but it really describes an archaeologist’s suspicion that Stone Age people in southwestern England built a ring—not an arc, as the name suggests—of Stonehenge-like circles of rocks in the Devon uplands. With the help of volunteers excavating at Dartmoor National Park, the researcher has just announced new findings that further support this idea.

“I can finally reveal some major discoveries that I have made during the course of my PhD fieldwork in the area of Taw Marsh, near Belstone, including two stone circles, a possible long cairn and a dolmen,” Alan Endacott, an independent archaeologist studying for a doctorate in archaeology at the University of Exeter in England, says in a Facebook post.

Endacott has been searching for stone circles on Dartmoor since the 1970s. His “sacred arc” theory led him to a discovery termed the Sittaford stone circle in 2007. Building on this idea, he looked for other related Stone Age locations.

“I first identified the ‘new’ sites in 2011, while following my theory that a ring of stone circles encircled the central high ground, continuing the arc of circles to the north and east,” Endacott explains on social media.

Alan Endacott next to some of the recently discovered stones Alan Endacott via Facebook

He ended up uncovering two stone circles estimated to be about 5,000 years old, making them contemporaries of the central part of Stonehenge. Like Stonehenge, archaeologists believe the structures were further modified during the Bronze Age, as Kirstie McCrum writes for Devon Live.

One of the newly found structures, which Endacott called Metheral after a nearby hill, is oval-shaped and spans 130 feet by 108 feet, he explains in another post on Facebook. It’s composed of 20 stones, though most have toppled over, with each up to 40 inches in height. They also found hints to the past presence of more stones.

Significantly, the Metheral circle seems to align with seven other stone monuments in the shape of a half-circle, supporting the sacred arc theory. It sits on the opposite end of the arc from the Sittaford site.

About a hundred miles northeast of Metheral lies the iconic Stonehenge—and despite that distance, Endacott suggests Stonehenge’s builders could have contributed to the construction of Metheral, as well, he says to Live Science’s Tom Metcalfe.

“People moved long distances in that period, so the people who built the stone circle at Metheral might also have been to Stonehenge and even possibly to Orkney,” Endacott tells the Guardian’s Steven Morris. “They traveled quite widely; there were lots of contacts between them with trading and so on.”

He adds that the team found hints of an earthen bank encircling the Metheral circle: a feature that has been identified in other Neolithic monuments, including in Cornwall and on Orkney in Scotland, in addition to Stonehenge itself.

Members of the excavation team, with Alan Endacott second from left Alan Endacott via Facebook

The team found the second stone circle, which Endacott called Irishman’s Wall after a nearby historical feature of the same name, about a mile north of the Metheral circle, and they uncovered six intact stones, per Live Science. The Irishman’s Wall position doesn’t align with the arc, though Endacott speculates that “maybe it was an entrance point [to the arc] from the north,” he tells the Guardian.

“This ‘arc’ of circles, measuring more than eight kilometers [five miles] across, is rather extraordinary and suggests the upland area of northern Dartmoor it encloses was particularly special to prehistoric people,” Susan Greaney, an archaeologist at the University of Exeter in England who was not involved with the discovery, tells Live Science.

In the Irishman’s Wall vicinity, the team also uncovered a collapsed dolmen, or a prehistoric structure with standing stones holding up a capstone. Endacott termed this discovery the “Fallen Brother dolmen,” in honor of the individuals from Dartmoor who lost their lives during World War I and World War II.

He adds on Facebook that teams collected samples for dating and analysis of the environment over time. Results from these tests, which are not available yet, could reveal even more information about the sites.

“These excavations exceeded my expectations and brought new evidence to light that will help with our understanding, but inevitably they have also raised more questions about why they were built,” Endacott tells the Guardian. “There are definitely other sites that I want to follow up on. We won’t be stopping any time soon.”

After all, if the theory proves to be true, that could mean the other half of the sacred arc is still out there to be found.