“Babylon”, opening imminently at the British Museum, is a vigorously revisionist, thoroughly engrossing and ultimately shocking exhibition. The show’s subject, in the words of curator Irving Finkel, is “a place that has become utterly remote in reality, yet remains ubiquitous in the imagination.” Babylon, once the greatest city in ancient Iraq, former capital of King Nebuchadnezzar, is historically distant indeed – more than two and a half millennia of devastation, decay and pillage have seen to that. But the city continues to live the most vivid of afterlives, in myth and in folk memory.

The mythical “Babylon” is synonymous with corruption and godlessness, and with a brilliant ingenuity fatally undermined by hubris. It is the city that produced the famous “hanging gardens”, once one of the seven wonders of the world. But it is also the site of the Tower of Babel, that storied attempt to reach to the heavens, which brought only fracture and division (according to the Book of Genesis, the babble of many tongues, the different languages of fallen man, were to be attributed to the tower’s collapse). It is the city identified, in the Judaeo-Christian tradition, with captivity and cruel conquest, with evil autocracy, with rulers weighed in the balance and found wanting – tyrants punished by God and even driven mad. To Jews and Christians alike, Babylon is where the chosen people lay down and wept. It is also “the whore of Babel” in the Book of Revelations, the evil empire that must be overthrown if good is to prevail. Rastafarians see it in the same symbolic light. One of the aims of reggae music is incantatory, the chanting down of “Babylon”.

To say the city has had a bad press would be an understatement. But the great fascination of the British Museum’s show lies in the extent to which Irving Finkel and his fellow curators have managed to assemble actual archaeological evidence – ranging from sculptures to maps to cuneiform tablets – against which to test the many myths of Babylon against the true, historical reality.

The exhibition opens with the images of a snarling lion and prancing dragon that once guarded the city, each one a glazed brick relief borrowed for the present occasion from the State Museums of Berlin. They are two mere tesserae from the mosaic of an entire civilisation, but still they conjure up the might and majesty of the city as it was in the time of Nebuchadnezzar – a man who deserves to be remembered, Finkel argues, “as one of the most extraordinary rulers – and builders – of the entire ancient world.

The wonders of Babylonian engineering remain the subject of intense speculation on the part of archaeologists and historians of science. It seems unlikely that the secret behind the fabled “hanging gardens” of the city will ever be discovered. But the fact that some kind of apparently miraculously irrigated gardens did once exist there is indicated, not only by several contemporary descriptions written by Greek travellers, but by the known expertise in aquatic engineering common to all the peoples of ancient Mesopotamia – literally, the land “between rivers”. The closest approximation to the hanging gardens, in art, comes in the form of an Assyrian rather than Babylonian relief – a tablet of delicately incised gypsum, created in Nineveh in the seventh-century BC, revealing fertile plots of cultivated land arranged in tiers descending from the side of an aqueduct. Nearby, a pair of cuneiform tablets turn out to contain a list of plants in a royal garden of Babylon, just before the time of Nebuchadnezzar. Coriander, beetroot and rocket are included, as well as one or two less well known delicacies such as “halla-issur” and “qinnat andi” – which are translated, in the learned catalogue to the exhibition, as “bird dung plant” and “slave girl-buttock plant” respectively. Babylonian salad ingredients were clearly nothing if not various.

Boldly disentangling myths from actualities, the exhibition goes on to explore the truth behind the fantastical tower of Babel. The tower’s prominent place in the western historical imagination is represented by a rich anthology of paintings, drawings and prints. The most celebrated painting of the tower, that by Bruegel, could not be lent to the exhibition because of its extreme fragility. But Bruegel’s work, for all its fame, is the merest tip of the iceberg when it comes to imaginary depictions of the tower. The British Museum’s exhibition contains a brilliantly fanciful pair of sixteenth-century engravings by Phillips Galle after Maarten van Heemskerk, giving a “before and after” view of the great construction rising, then crashing to the ground. Also included is a copy of Athanasius Kircher’s eccentrically ingenious late seventeenth-century text, Turris Babel, an attempt to synthesise all existing knowledge of the Tower of Babel. The page is open at an illustration by Conraet Decker entitled Demonstration of the Impossibility of Building a Tower to Heaven, in which the globe of the earth is shown, in cross-section, with a tower so enormous protruding from it that it resembles nothing so much as a bald, beaked bird. In illustration one, the beak-like tower sticks straight up in the air; in illustration two, it sets the world awry on its axis. It is a strangely rational, mechanical demonstration of the impossibility of scaling the heavens.

The Tower of Babel may never have existed, but the idea of it was based on a structure that was actually built – the great Etemenanki, the ziggurat dedicated to Marduk, god of the Babylonians. Proof positive comes in the form not only of the archaeological site of Babylon itself – aerial photographs reveal the vast foundations of the ziggurat, bordered by what is now no morew than a rectilinear network of ditches filled with brackish water – but in the shape of a small cuneiform tablet loaned by the Louvre’s department of oriental antiquities. The Esagil tablet, as it is known, is a set of mathematical exercises designed to help Babylonian engineering students to calculate the appropriate ratios between the height and the base of a building. All of the exercises are based on the real ratios used in the building of the great ziggurat – which prosaically, turns out to have been levelled not by God but by the Persian ruler Xerxes, to suppress a Babylonian revolt long after the fall of the Babylonian empire.

The Babylonian captivity, so hauntingly described in Psalm 137 – “By the rivers of Babylon, there we sat down, yea we wept, when we remembered Zion” – also receives some fascinating revisionist attention. The forces of Nebuchadnezzar certainly did conquer Jerusalem and take the city’s people into captivity – one tiny little clay tablet written by a Babylonian scribe at the very moment of the events tells the story in terms remarkably close to the Old Testament account, while another even lists the rations to be given to the captive Jewish king and his retinue. But the idea that this was purely and simply an evil time for the Jewish peoples is called into question. The Babylonian religion, centred on Mahduk, was essentially monotheistic, and the exhibition contains a tablet reflecting on the nature and meaning of monotheism by a Babylonian religious writer. Since the Babylonian captivity took place when Jewish theology was itself in a state of flux, it seems likely that Jewish monotheism was itself shaped, to some degree, by Babylonian thinking.

There is a vast amount of food for thought in this visually and intellectually stimulating exhibition; and all kinds of ancient mistakes and misidentifications are put right. It was not Nebuchadnezzar who went into exile, but his successor Nabonidus. So the figure famously traduced by William Blake, in his famous large drawing of the exiled Nebuchadnezzar in his supposed madness, shown as a man on the verge of turning into an animal – turns out to be a flight of fantasy based on a case of mistaken identity. Truth is more complicated than fiction, too, when it comes to the Book of Daniel. With its stories of Daniel in the lions’ den, Daniel the interpreter of dreams, the Old Testament paints the picture of a coolly superior Jewish intellectual, shining beams of enlightenment into the dark and superstitious world of his Babylonian captors. But in fact the Babylonians educated their Jewish captives in a whole host of subjects, ranging from mathematics to celestial geometry, so it seems likely that what David truly symbolised was a new, post-Babylonian culture of enlightened jewry. His people learned, as well as wept, by the rivers of Babylon.

The moral of the exhibition as a whole is that the Babylonian legacy to the world of the Near and Middle East was rich, vital and vigorous, in all kinds of ways which archaeologists and scholars are still attempting to explore. That makes the conclusion to the show doubly saddening. Here, the visitor learns of the enormous damage done to the site of ancient Babylon by Saddam Hussein – who fancied himself a second Nebuchadnezzar and actually rebuilt whole sections of the city, in what looks like breezeblock concrete, directly on top of the archaological site itself. The vandalism has not ended there. Nowadays, the ancient site of Babylon is occupied by an American military base. Recent photographs – the exhibition ends with a grim slide show – reveal a helipad right next to the ancient Processional Way (which has been additionally damaged, apparently, by the passage of heavy armoured vehicles); as well as what another caption simply describes as “An anti-tank trench dug through archaeological deposits at Babylon”. The time really has come – as this exhibition compellingly demonstrates – for the senseless destruction to stop. It is earnestly to be hoped that the American Ambassador will take time to visit the British Museum in the very near future.