The Hanging Gardens of Babylon, one of the Seven Wonders of the Ancient World, weren't in Babylon at all - but were instead located 480km to the north in Babylon's greatest rival, Nineveh, according to a leading Oxford-based historian.
After more than 20 years of research, Dr Stephanie Dalley, of Oxford University's Oriental Institute, has pieced together enough evidence to prove beyond reasonable doubt that the famed gardens were built in Nineveh by the great Assyrian ruler Sennacherib - and not, as historians have always thought, by King Nebuchadnezzar of Babylon.
Dalley first publicly proposed her idea that Nineveh, not Babylon, was the site of the gardens back in 1992, when her claim was reported in the Independent - but it has taken a further two decades to find enough evidence to prove it.
Detective work by Dalley - expected to be published as a book by Oxford University Press - has yielded four key pieces of evidence.
First, after studying later historical descriptions of the Hanging Gardens, she realised that a bas-relief from Sennacherib's palace in Nineveh portrayed trees growing on a roofed colonnade exactly as described in classical accounts of the gardens.
That crucial original bas-relief appears to have been lost in the mid-19th century. When it was discovered by the British archaeologist Austin Henry Layard in the 1840s, it seems to have already been in such poor condition that its surface was, in all probability, rapidly crumbling away.
Alternatively, it may have been among a group of Layard's UK-bound Nineveh carvings which were lost when the boat carrying them sank in the River Tigris. Luckily, however, an artist employed by Layard had already drawn the bas-relief - and that drawing, recently recognised by Dalley as portraying the garden, had been reproduced in Layard's book about Nineveh, published in London in 1853.
Further research by Dalley then suggested that, after Assyria had sacked and conquered Babylon in 689 BC, the Assyrian capital of Nineveh may well have been regarded as the "New Babylon" - thus creating the later belief that the Hanging Gardens were in fact in Babylon itself.
Her research revealed that at least one other town in Mesopotamia - a city called Borsippa - was being described as "another Babylon" as early as the 13th century BC, thus implying that in antiquity the name could be used to describe places other than the real Babylon.
A breakthrough occurred when she noticed from earlier research that after Sennacherib had sacked and conquered Babylon, he had renamed all the gates of Nineveh after the names traditionally used for Babylon's city gates. Babylon had always named its gates after its gods. After the Assyrians sacked Babylon, the Assyrian monarch simply renamed Nineveh's city gates after those same gods. In terms of nomenclature, Nineveh was in effect becoming a "New Babylon".
Dalley then looked at the comparative topography of Babylon and Nineveh and realised that the totally flat countryside around the real Babylon would have made it impossible to deliver sufficient water to maintain the sort of raised gardens described in the classical sources. As her research proceeded it therefore became clear that the Hanging Gardens as described could not have been built in Babylon.
Finally her research began to suggest that the original classical descriptions of the Hanging Gardens had been written by historians who had visited the Nineveh area.
Researching the post-Assyrian history of Nineveh, she realised that Alexander the Great had camped near the city in 331BC - just before he defeated the Persians at the famous battle of Gaugamela. It's known that Alexander's army camped by the side of one of the great aqueducts that carried water to what Dalley believes was the site of the Hanging Gardens.
Alexander had on his staff several Greek historians including Callisthenes, Cleitarchos and Onesicritos, whose works have long been lost to posterity - but significantly those particular historians' works were sometimes used as sources by the very authors who several centuries later described the gardens in works that have survived.
"It's taken many years to find the evidence to demonstrate the gardens and associated system of aqueducts and canals were built by Sennacherib at Nineveh and not by Nebuchadnezzar in Babylon.
"For the first time it can be shown that the Hanging Garden really did exist" said Dalley.
The newly revealed builder of the Hanging Gardens, Sennacherib of Assyria - and Nebuchadnezzar of Babylon who was traditionally associated with them - were both aggressive military leaders.
Sennacherib of Assyria destroyed the great temples of Babylon, an act which was said to have shocked the Mesopotamian world.
Bizarrely it may be that the Hanging Gardens were the first of the seven "wonders" of the world to be so described - for Sennacherib himself referred to his palace gardens, built in around 700BC or shortly after, as "a wonder for all the peoples".
The new research has finally revealed that his palace gardens were indeed one of the Seven Wonders of the Ancient World. Some historians have thought that the Hanging Gardens may even have been purely legendary. The new research finally demonstrates that they really did exist.