The father of civilisation: Alexander the Great's hunger for knowledge gave us everything from the Old Testament to algebra and even robots



There is not, and has never been, another city to match it. It was a glittering metropolis, home to the most sexually charismatic queen of all time, founded by a man whose megalomaniac ambitions knew no bounds.



It was a buzzing hub that boasted one of the seven wonders of the world, where intellectual geniuses from both East and West met to tussle and debate in a library containing all the knowledge on the planet.



Founded more than 2,300 years ago, and in its hey-day one of the most powerful places in the world, this is now a lost city, most of it buried beneath waves off the coast of modern Egypt.

Alexander the Great: The Greek leader made Alexandria a place of knowledge, discovery and sexual intrigues

This is the city of Alexandria. By rights, Alexandria should be a household name, as famous as Athens or Rome. Make no mistake, this was a metropolis as beautiful as Paris, as creative as London, as hip as New York and more learned than Harvard.



And yet, as I discovered while researching a new documentary, somehow this amazing urban experiment is just a footnote in history.



Luckily for us, the secrets of this wonder of the ancient world are being unearthed, as archaeologists uncover more and more from its lost treasures.



Alexandria is irresistible. It aches with harsh romance. It was home to sexual intrigues, to treacherous power-grabs and to the birth of religious fundamentalism.



Caesar, Cleopatra, Mark Antony, Euclid, Galen, Archimedes all walked its streets. For its wild and heady festivals, Alexandrian inventors would construct brilliantly eccentric 'living machines' that roamed the elegantly appointed, granite-paved streets.

Steam-powered lions, trees full of singing mechanical birds, once even a house-size snail that trailed fake slime on the flagstones as it slithered along - these were all created to wow the Alexandrian populace and dumbstruck visitors.



Here Cleopatra's ancestors paraded an 80ft phallus tipped with stars towards a 120ft round, gem-encrusted wreath.



Little surprise Alexandria was a city for such heady flights of fancy - given that it was founded because of a dream. In around 332BC, the Greek leader Alexander the Great - so-called because his audacious plan was to take over the known world - had a vision.



Tossing and turning in bed one night, perhaps disturbing his bedmate (a boy or a girl - Alexander's prodigious sexual energy meant he loved both), an old, bearded man appeared to him.



The story went that this was the ghost of Homer, and he pointed the young Greek king towards a mysterious place called Pharos.



Alexander's generals got out their maps. Pharos was an island off the rugged coast of Egypt. This was where the mighty conqueror would found the centre of his new world.

Treasures in the deep: Many ancient artefacts, like this statue, are submerged in Alexandria's eastern harbour in Egypt

Alexander the Great had already won over Egypt, through a 'hearts and minds' campaign. Whereas the Persians had previously fire-stormed through the region, torching temples, beheading priests and intimidating locals, Alexander's approach was softly, softly.

Worship your god in the shape of a mummified bull? No problem, he told the locals, I will too. Believe your leaders are living gods? I can be the greatest living god of them all, he vowed.



As a result, his colonisation of Egypt was swift and absolute. Within a few years, Alexandria was the capital of Egypt - and Alexander was its ruler.



And so Alexandria became a show city of the future. Its architects had laid out the street plan by scattering barley-flour in a grid-pattern on the sand.



And when it was built, grand central avenue was lined with street lights fired with olive oil and flanked by theatres, markets, lecture halls and giant temples - one of which could be seen for miles out to sea.



Cisterns brought fresh water to all quarters of the city. There was a zoo and the world's first museum. One visitor declared: 'It is impossible to describe it adequately, but the city is so adorned with immense columned courts, life-like statues, and a multitude of other great works that, save for the Capitol [in Rome]…the world can offer nothing more magnificent.'



But this wasn't a city built just for display. Because Alexander believed that he should, and could, conquer the world, his generals set about acquiring for him the kind of knowledge that would make him supremely powerful.

Anthony and Cleopatra: The famous couple, immortalised on film by Richard Burton and Elizabeth Taylor, were at home in the metropolis of Alexandria

As time went on, special agents were dispatched in ships to collect precious documents from far and wide. Philosophies, plays and great works of literature were brought back.



But much of the information collected from the four corners of the world was brilliantly pragmatic. And so here linguistic codes were cracked, water-clocks and steam-engines invented and great discoveries made.



Alexandrians built the first robot, which clanked its way through the theatres of the city, powered inside by carefully controlled falling sand.



They gave us the first automatic doors (using a complicated system of hydraulics and pulleys, temple doors would 'magically' swing open). They developed a primitive form of jet power, using tiny steam-shafts that kept objects hovering in the air as if on invisible strings.



They even gave us the first slot machine, which dispensed holy water to delighted worshippers.



A huge library was built to house this sum of human knowledge. At its height it contained between 500,000 and 750,000 books.



Scribes assiduously copied one tome after another. The scratch of their reed pens on papyrus filled the air, and they came to be known as the 'chatterers'.



With such intellectual stimulus on offer, the city soon attracted the finest minds from across the globe. The mathematician Eratosthenes flourished here, and by simply watching the changing lengths of the Egyptian sun's shadows, he measured the circumference of the Earth.



Bloodthirsty and hungry for knowledge: Alexander, seen here portrayed by Colin Farrell, planned to take over the known world

His calculation was 24,662 miles - just less than 200 miles short of the true figure.



Another sage, Aristarchus, proved that the Earth revolved around the sun and understood, way before others, that the Earth, sun and moon had to be seen in relation to one another if they were to be measured.



Soon after, Euclid devised the system of geometry that still torments our schoolchildren today. This was also where the Old Testament was preserved for future generations.



It was said that 72 of the best scholars who spoke both Hebrew and Greek worked for 72 days in 72 separate cells to translate the old testament texts into Greek.



Their efforts - named then and today 'the Septuagint' - were not wasted. The Old Testament only survives into the 21st-century thanks to the men of Alexandria in the 2nd-century BC.



Medicine was pioneered here, too. If you had walked through the public lecture rooms that pock-marked the city, you might have found eager young doctors performing unspeakable experiments on animals to prove their theories.



One man, Galen, revolutionised neuroscience under that hot Egyptian sun. He proved that the brain is the pinnacle of the central nervous system, and that feelings stem from our mind rather than our heart.



These were breakthrough discoveries. Galen ended up court doctor to the Caesars, operating on traumatised gladiators, whose wounds he described as 'windows into the body'.



But it was Alexandria -with its unique mix of Egyptian, Roman, Greek and Eastern influences - that really allowed Galen to flourish.



Through much of the Eastern Mediterranean, people were a bit squeamish about human innards. Tampering with all that oozy material was taboo: thought to infect the air, to create a miasma of pollution. The brain, for instance, was viewed as rather disgusting.



But since Egyptians loved their mummification (they would pull the brain out through the nose to stop it rotting in the skull) Galen was able to indulge in high-end dissection.



Organs and body parts were easily available here. His anatomical discoveries about the human body - and the aid this brought to thousands of sick men and women across the world - would not be bettered for 1,500 years.



Indeed, it is only by comprehending what an intellectually brilliant city Alexandria was that the famous story of Queen Cleopatra makes sense.



Although this ruler of Egypt clearly was a woman of enormous physical charisma, she was not just an ancient pin-up, but a highly intelligent philosopher and a mathematician.



It could be that Cleopatra killed herself not just because she did not want to be paraded through the streets of Rome as a prisoner of war, but because the idea of life in any city other than Alexandria was simply unbearable.



The theatricality of the great queen's death is strangely appropriate for the city.



Today, to get up close to the Alexandrians your best bet is to descend 35 meters into the Earth to Alexandria's necropolis - a city of the dead.



Down there, Alexander is almost certainly buried, and for centuries his body was on display within a crystal-cut coffin.



You can still walk through the catacombs, through subterranean rock-cut colonnades, gorgeously ornate, under the watchful eye of sphinxes, Medusas and Pharonic eagles (the symbol for Egypt even today). Tombs here are guarded by dog-headed centurions.



Cleopatra's Needle: A piece of Ancient Alexandria that stands on the Embankment in London

But thanks to earthquakes and subsidence, vast areas of Cleopatra's palatial complex have disappeared beneath the modern port of Alexandria.



When I was there just a couple of weeks ago, one archaeologist excitedly pointed to the torso of a 30ft high statue - lying, seaweed covered, on the sea bed. There are many hundreds of other treasures, just eight metres or so beneath the surface of the water, waiting to be excavated.



But oddly for us Brits, there is a splendid fragment of Alexandria still visible in the UK, day in day out.



It is a red-granite Egyptian obelisk, now affectionately known as Cleopatra's Needle, which stands on the Embankment in London. Originally dating from 1,450 BC it was bequeathed to Britain by Egyptians grateful for Nelson's part in quelling Napoleon's ambitions to control Africa.



Cleopatra's Needle was witness to both the brilliance and brutality of Golden Age Alexandria. It was, in fact, witness to an horrific murder.



One of the neglected, mysterious characters of Alexandria, who is at last getting the recognition she deserves (in books and a new film starring Rachel Weisz) is a woman called Hypatia.



A mathematician and philosopher, Hypatia ran the great philosophy school of the city where pagans, Jews and Christians studied together. She was a famed beauty, with a beautiful mind.



Obsessed with the journey of the stars, she used her mathematical and geometrical knowledge to try to map them, and deduce why the Earth revolved around the sun.



But as the years went on, and a new puritanical force appeared in the city, Hypatia's studies were deemed dangerous - an unnatural, demonic pursuit.



Although Alexandria had been a remarkably tolerant place, men and women from East and West, pagans, Christians and Jews allowed to work alongside one another, one faction of the fledgling Christian church wanted total political control of the city.



Hypatia was on her way back to her house one afternoon, when she was dragged from her carriage and stripped naked. For a noble-born woman this was a terrible disgrace.

But then things got worse. The mob pulled her into the nearby temple - originally built for Caesar and recently converted into a church - where they flayed her alive with pieces of broken pot and roof tiles. Still not satisfied, they tore her limb from limb and burnt her body parts at the edge of the city.



To all intents and purposes this was a witch's death. Hypatia's assassination marks the end of an epoch. The end of the ancient, pagan world - and the beginning of the troubled, modern era.



From the death of Hypatia onwards, rival factions battled for control of the city. In 641 AD, as Arab forces swept along the coast, what was left of Alexandria's great libraries were burnt in a whirlwind of battle fires.



Today, we have just 1 per cent of its contents. The rest has been lost for ever.



Alexandria begins as a fairy tale and ends a horror story. For this reason alone, we should not bury its memory.



Bettany Hughes on the Ancient World is available online at www.channel4.com/4od



