The Altar Stone at the heart of Stonehenge came from the North-east of Scotland rather than south-west Wales as previously thought, new analysis has found.
The discovery shows the construction of Stonehenge was a far greater collaborative effort than scientists realised.
It also means that the ancient monument, near Salisbury in south-west England, was built with stones from all parts of Great Britain.
The findings suggest Neolithic Britain was a far more connected and advanced society than earlier evidence indicated.
The distance between Stonehenge and the far north of Scotland is about 700km (434 miles).
The research was led by a Welsh PhD student, Anthony Clarke, now working at Curtin University in Western Australia.
The bluestones at Stonehenge were identified as coming from the Preseli hills in Pembrokeshire in 1923, by Welsh geologist Henry Herbert Thomas. The central Altar Stone was made of a different rock but always assumed to have come from the same area, until 20 years ago when scientists first began to question its origins.
Last year, researchers including Prof Nick Pearce from Aberystwyth in Wales, of all places, concluded that the Altar Stone could not have come from Wales. But its origin had remained a mystery, until now.
“It blew our socks off when we discovered it was from north-east Scotland,” Prof Pearce, who was also involved in the current discovery, told BBC News.
“It was a shock to say the least. Coming from that distance, more than 700km, was remarkable.
“The Neolithic people must have been pretty well connected, far more connected than people give them credit for. They must have been very well organised”.