He was a tourist in Rome, seeing the sprawling ruins wormholed by time. He probably heard shots at the Forum: its crumbling stones, overgrown with long grass, were popular with hunters. The Colosseum, meanwhile, with its oval facade and labyrinth of tunnels and buttresses, struck him as having the scale of a city. And over the river, the building site that was to become St Peter's Basilica was so gargantuan, it added to his idea of cities as deranged architectural enterprises.
Pieter Brueghel made a painting on ivory while he was in Rome, of a stupendous building. It is now lost. Later, back home in Flanders in 1563, he responded to Rome's sights, using the Colosseum as his model. The result was a great painting that today hangs in the Kunsthistorisches Museum, Vienna. Beside a blue sea, a medieval town, with its clapboard houses, church spires, red rooftops and plump little people, has settled comfortably into a wide green plain. It is a vision of cosiness and habit - but this town has cancer.
That does seem an appropriate image: this colossal tower grows without constraint, without purpose, its scale revealed by the little houses below, whose ordinariness makes visible its extraordinariness. Seven arcaded tiers ascend from a fat, round base. A road spirals round, swarming with workers, cranes, little houses like parasites. In its gaping heights, ribs of stone are exposed and dark doors lead into its core. Still more storeys are being created, a second tower emerging from the first. An outsized, out-of-control plaything, this building seems determined to swallow the world.
The Tower of Babel is a vision of architecture as anthill madness. As the British Museum's exhibition Babylon: Myth and Reality reveals, Brueghel is not the only artist driven to imagine this fabulous building. Towers of Babel proliferate in this show, be they painted with miniaturist precision or exploding in apocalyptic doom; there's even one made of shoes, in a 2001 painting by Michael Lassel. Martin van Heemskerk's, however, is square, in keeping with old sources he studied, but his attempt to visualise what the tower was "really" like does not stop him showing its top smashed apart by divine lightning. In an anonymous Dutch painting - one of a series that riff on Brueghel - the city that surrounds the tower is on fire, the summit of the hubristic edifice menaced by an eerie light coming through the storm clouds. Perhaps the strangest is by Athanasius Kircher, a 17th-century scholar whose light, airy spiral looks prophetically modern, like a blueprint for a skyscraper.
These fascinating images are attempts to illustrate the greatest story ever told about a building. The tale is in the Bible. After the Flood, the descendents of Noah spread over the earth, and resolved to build a city and a tower, whose top reached "unto heaven". The Lord was not too pleased. For if people can do this, "nothing will be restrained from them". He smote their hubris, scattered them abroad and confounded their language: until then, everyone had spoken the same tongue, but now a multitude of tongues confused them and they gave up building their city and their tower.
The story of the Tower of Babel stands at the heart of how we imagine architecture. This myth hovers over every tall building; behind all criticism of skyscrapers lurks the spectre of Babel, smote for its hubris. It is a great myth but the British Museum's show reveals it is a true story. The real Tower of Babel is the first thing you see as you enter the show - or rather you see its footprint. In an aerial photograph taken by Georg Gerster in 1973, the dark square mark of the tower's foundations, and that of the staircase that ascended it, can be seen in bright dust near the fertile Euphrates. This is the site of the ancient city of Babylon in Iraq. That black square was left by a huge ziggurat, a tower whose width diminishes as it rises, invented by the architects of ancient Mesopotamia. The Bible even gets the material right: it was built of fired bricks. You can see one on display marked with the name of Nebuchadnezzar, who ruled Babylon in the sixth century BC.
His Babylon was a place to inspire dreams, a daunting, dazzling city. You can see that from the reliefs of lions and a magical dragon that loom over a model of the city's grandiose Ishtar Gate. If the Tower of Babel is an imaginary version of a real building in Babylon, the Ishtar Gate - dedicated to the Mesopotamian goddess of love and war - is solid and real. In the late Victorian age archaeologists found the lost city of Babylon near Baghdad, and a team of German archaeologists excavated it in the early 1900s. If you visit Berlin's Pergamon Museum, you can see the massive blue gate they found.
This show compares the myths of Babylon with the real city revealed by such archaeologists. Exhibitions with this type of postmodern premise can be frustrating, especially when they don't include the most famous images: Brueghel's Tower is not here, nor is Rembrandt's Belshazzar's Feast, although it's not far away, at the National Gallery. So why does this exhibition still manage to be so compelling? Because the reality is as beautiful as the myths. A dragon of glazed bricks, with a snake's head, lion paws and eagle talons, strides through deep blue space, just one of many strange beasts that decorated the city gates and processional ways. You can look from Dutch paintings of the tower to a model showing how archaeologists reconstructed the real-life ziggurat, already a very old architectural design by the sixth century BC.
Ziggurats were built as stairways to heaven. A god could come down to earth via this tower, and priests could go up to sacrifice direct to the gods. But if this was so, why was it rendered as an arrogant, hubristic tower that offended God? Because in the sixth century BC, the Babylonians conquered Jerusalem and took its king and other people hostage, and this event is remembered in the Bible as one of the deepest oppressions of God's chosen people. Like the Tower of Babel, the "Babylonian Captivity", related in the Book of Daniel and Psalms, is rooted in history. The Jews saw Babylon as a city of sin, pride and luxury. It appears again and again in the Bible, its desolation prophesied by Isiah and personified in the Book of Revelation as the Whore of Babylon.
The show features Albrecht Dürer's hallucinatory vision of the Whore of Babylon, along with William Blake's depiction of Nebuchadnezzar crawling on the ground, reduced to grass-eating madness, his punishment according to the Book of Daniel. These images bring to life the static artefacts of ancient Mesopotamia that are shown beside them, such as the clay tablets beautifully incised with cuneiform letters. Myth illuminates reality - and that reality lives on in our world far more than we appreciate. Astrology, for example, is a Babylonian invention. Here you can see how the Babylonians invented the zodiac and how it was taken up by Islamic and European stargazers, and led to astronomy.
At the end of the show, the damage done to the archaeological site in the Iraq war is documented. The British Museum protested at the use of the site for a military base - the helicopters landing in the middle of such a precious site, the soldiers vandalising it in search of souvenirs. The images are chilling, as eerie and apocalyptic as anything in the show.
Babylon: Myth and Reality is at the British Museum, London WC1 (020-7323 8181), from Thursday to March 15.
· This article was amended on Wednesday November 12 2008. It is the Book of Revelation, not Revelations as we said in the article above. This has been corrected.