The origin of the giant sarsen stones at Stonehenge was eventually discovered using a missing piece from the site that was returned after 60 years.
A one-meter-long core test was paired with a geochemical study of standing megaliths.
Archaeologists have identified the source of the stones in an area 25 km north of the site near Marlborough.
Susan Greaney of English Heritage said the find was “a real thrill”.
The seven-meter-high sarsens, which weigh about 20 tons, form the fifteen stones of the central horseshoe of Stonehenge, the uprights and lintels of the outer circle, as well as the peripheral stones.
The smallest blue stones in the monument have been attributed to the Preseli Hills in Wales, but the sarsens have been impossible to identify until now.
The return of the nucleus, removed during archaeological excavations in 1958, has enabled archaeologists to analyze its chemical composition.
No one knew where he was until Robert Phillips, 89, involved in the work, decided to return part of it last year.
The researchers first performed x-ray fluorescence tests of all the remaining sarsens at Stonehenge, which found that most shared similar chemistry and came from the same region.
They then analyzed the sarsen outcrops from Norfolk to Devon and compared their chemical composition with the chemistry of a piece of the upturned core.
English Heritage said the opportunity to do a destructive test on the nucleus turned out to be “decisive”, as it showed its composition to match the chemistry of sarsens at West Woods, just south of Marlborough.
Professor David Nash of the University of Brighton, who led the study, said: “It has been truly exciting to harness 21st century science to understand the Neolithic past, and finally answer a question archaeologists have been debating for centuries.
“Each outcrop turned out to have a different geochemical signature, but it was the opportunity to test the overturned core that allowed us to determine the source zone of the Stonehenge sarsens. ”
Ms Greaney said: “Being able to locate the area that the builders of Stonehenge used to source materials around 2500 BC is a real pleasure.
“While we suspected that Stonehenge’s sarsens were from the Marlborough Downs, we didn’t know for sure, and with areas of sarsen across Wiltshire, stones could have come from anywhere.
“They wanted the biggest, most substantial stones they could find and it made sense to get them as close as possible. ”
Ms Greaney added that the evidence points to “how carefully the construction of this phase of Stonehenge was studied and deliberated.”