The giant boulders that comprise Stonehenge have provided a sense of wonder for visitors and academics who come to visit the prehistoric monument in England.
Now, after centuries of debate by archaeologists, the origin of the large sarsen stones –also known as megaliths – have been traced just 15 miles away from the monument itself, near the town of Marlborough.
The breakthrough was published in the Science Advances journal Wednesday.
Stonehenge is built out of two types of stones: sarsen stones, which all 15 of the monument’s central horseshoe are made out of, and smaller bluestones, which have been traced to the Preseli Hills in Wales, per English Heritage.
The megaliths, each weighing tens of thousands of pounds and standing up to 22 feet tall, have never been tested.
But a restoration of Stonehenge more than 60 years ago required three stones in the monument to be re-erected. In order to ensure the integrity of one of the megaliths, which had a fracture through it, three horizontal holes were drilled.
The core material from these drillings was thought to be vanished until last year, when a man named Robert Phillips – who was present at the repairs – returned one of the cores to English Heritage.
Phillips, who now lives in Florida, wanted it sent back on the day before his 90th birthday.
After performing non-destructive tests on the sarsens at Stonehenge, researchers were able to determine that they all came from the same area. They then analyzed sarsen formations, or outcrops, across England.
"Each outcrop was found to have a different geochemical signature, but it was the chance to test the returned core that enabled us to determine the source area for the Stonehenge sarsens," said David Nash, a professor of geography at Brighton University.
After performing a destructive test on the returned core, they traced it back to an area known as the West Woods. These stones, English Heritage historian Susan Greaney said in a statement, were likely chosen because builders "wanted the biggest, most substantial stones they could find and it made sense to get them from as nearby as possible."
Scientists have yet to figure out the route and method they used to transport these gargantuan stones to their current location.
To complicate the mystery, two stones were obtained elsewhere, per the study published Wednesday. Still, this key discovery helps make sense out of this ancient mystery.
“To be able to pinpoint the area that Stonehenge’s builders used to source their materials around 2500 B.C. is a real thrill. Now we can start to understand the route they might have traveled and add another piece to the puzzle," Greaney said.
This article originally appeared on USA TODAY: Stonehenge study: Origins of large sarsen stones traced by researchers