I'm on the edge of Anatolia.
It's a Greek word. Greeks had lived here for thousands of years.
In Greek, it just means "the land where the sun rises".
But a thousand years ago, another people arrived here.
When they met people on the road, they'd say, "Where are you going?"
They would normally answer in Greek, "eis tin poli" - "to the city",
and that's how this city got its new name.
"Eis tin poli" - Istanbul.
Those people were the Turks.
And this is the story of how Greek Constantinople became Turkish Istanbul.
How the ancient capital of Christianity became the imperial city of Islam.
CALL TO PRAYER
I've come here as both historian and traveller...
..to find that story written into the fabric of the living city.
So far, I have uncovered its transformation from a small, pagan fishing village
to the Christian capital of the Roman Empire.
But that set it on a collision course with Rome itself
and with new forces to the east.
After 700 years,
this place had come on an incredible journey.
What happened over the next 400 years would define not just this city, but the world.
Now I want to get to the heart of that moment
when global history seemed to pivot
on the fight to possess and identify this one fickle city.
Byzantium, Constantinople, Istanbul -
three names for one totally extraordinary city.
It's been occupied by the Greeks, the Romans, the Byzantines, the Venetians and the Turks.
It's been a world city, a cosmopolitan city, a capital of empires.
It owes its place to its unique position astride Europe and Asia,
but also to its history
as a holy city and an imperial capital.
Constantinople in AD 1000 -
the new Rome.
For 700 years, this city had been the capital
not just of an empire, but of a religion,
a different kind of holy city.
Holy cities are places where men encounter the divine,
but Constantinople was always different from Jerusalem or Mecca,
the settings of the great dramas of the monotheistic religions.
When Constantine the Great converted to Christianity,
he made Constantinople the capital of his unified Christian empire -
one faith, one empire, one emperor.
A fusion of power and sanctity.
This was a new idea. Jesus had been a carpenter's son
and now this was a city of sacred emperors.
And it defined one thing.
The possession of Constantinople gave you God's authority to rule the world.
Constantinople was about religion and power.
It was a heady cocktail coveted by every empire that came after it.
And over the centuries, two great rivals emerged
with their own ambitions to rule the world for God -
the Caliphs of Islam and the Popes of Rome.
The fall of Constantinople to Islam is one of the great stories of world history,
but what is less well known
is that the real story of the death of Byzantium began 400 years earlier in AD 1054.
Not with a conflict between Christians and Muslims,
but a war of words between Christians and other Christians.
The story unfolded in the sacred heart of this city -
its awesome cathedral, Hagia Sophia.
It was more than 500 years old at the turn of the millennium.
And even today,
it's still one of the most awe-inspiring buildings on Earth.
This was the holy of holies of Byzantine Christianity,
the place where, ever since the fall of Rome,
emperors had been crowned
who claimed rightful sovereignty over every soul in Christendom.
But in 1054, the peace of this building and that universal vision were shattered...
..by the agents of Byzantium's resurgent, ancient rival -
Rome.
On July the 16th, papal legates burst into the service here in Saint Sophia
and laid a sentence of excommunication right on the altar.
Four days later,
the Orthodox Patriarch of Constantinople excommunicated the papal legates.
It seemed like just the latest skirmish in centuries of ecclesiastical bickering,
but in fact, this time, it would bring total catastrophe to the city.
They called it the Great Schism,
the moment Christianity split into two rival camps.
On one side were the Byzantines, Greek-speaking, Orthodox,
and on the other, the Latins,
so called because they held services in Latin, not Greek.
But their differences went far deeper than language.
They disagreed on the fundamental nature of God.
But that was nothing compared to the cultural differences.
You can meet the Byzantine Emperors, appropriately enough, up in the gods.
In this high-up part of the church, you can almost feel the air becoming a bit more rarefied.
This is the Marble Gate and up here the Empresses would sit on their throne
and watch the services going on down below,
while over here, the Emperor and his entourage would arrive
via a secret passageway from the Great Palace.
There's no better place to get into the heads of the Byzantine side of the quarrel
because here you can come face to face with the person who was in charge
in the run-up to the Great Schism.
Here's Zoe.
Princess Zoe was a plain old spinster
who, crowned Empress in the autumn of her life, discovered the joys of sex
which she embraced with unabashed and brazen enthusiasm.
She married three times and each husband became Emperor.
You can see here that every time she remarried,
they had to rub out the head and rub out the name and put a new one in.
Now, the first husband exhausted himself taking aphrodisiacs to keep up with her,
but her minister, the sinister John the Eunuch, set her up with his teenage brother Michael.
Zoe fell passionately and head over heels in love.
She had her first husband murdered in her bath
and he was still lying there when she married her teenage lover Michael
who turned out to be actually a very good emperor.
But he died of exhaustion
and so she married for the third time -
Constantine, who we see up here.
But he had a problem. He was in love with his mistress Skleraina.
This didn't put off Zoe at all.
The three of them set up home happily in the Imperial Palace
where they lived together in a very Byzantine menage a trois.
It's a juicy story and it gets you into the heads of the Byzantine elite.
They were refined, elegant.
They loved strong women and they despised petty morality.
Down the hall, you can get a sense of what they thought of their upstart western rivals.
The Great Schism had divided Christendom
into two warring sects -
Roman Catholicism and Eastern Orthodox.
But the hatred wasn't just religious. It was also cultural.
And this graffiti here tells some of the story.
The Byzantines had really got to know westerners
through the arrival of the Varangian Guard,
the new Emperor's bodyguard made up of Norsemen and Vikings
and Anglo-Saxon mercenaries.
This is probably some of their graffiti.
Byzantines regarded themselves as the greatest civilisation history had ever known,
the Roman Empire and their Emperor as Christ's own vicegerents on Earth.
To them, the westerners were the sort of shaggy-haired axemen
who left graffiti in their favourite church.
Christianity was divided into two camps -
the Greek-speaking, effete, elegant Byzantines
and the hardy warrior culture of the Latin-speaking west.
But an amazing twist in the tale was coming.
Byzantium was going to need the west's hairy axemen more than ever before
because it was now facing a war on two fronts.
Just 17 years after the schism with Rome,
Christianity and Byzantium faced the greatest ever threat to their existence.
To the east, the Turks were sweeping into the Empire.
And in 1071, they destroyed the Byzantine Army.
It was the start of a new chapter
in Byzantium's history,
one in which the city would face enemies to both east and west.
No-one knew what was going to happen.
Islam had been on the march for 400 years
and the big question now was would Christendom, would Constantinople survive.
This was the beginning of a 400-year struggle
in which there were not two sides, but three
in the coming struggle that pitted the invading Turkish Muslims
against the two feuding sects of Christendom, east and west.
The big question now would be could they put aside their differences and unite to face the common enemy.
This was the last chance for Christian Constantinople
to use one enemy to fight off the other.
Of their two possible allies,
they chose the ones who were at least Christian.
The new Emperor, Alexios Komnenos, held his nose and sent an appeal to the Pope
for armed forces to counter the threat of the infidel.
He had hoped for a battalion or two of well-trained knights.
What he got was the Crusades.
It was as if the entire world of the west, from the Adriatic to the Straits of Gibraltar,
had come here to Constantinople
and the Crusades really were an extraordinary and enormous movement of people,
80,000 of them, some in unruly mobs and some in organised, princely armies,
but they all came here.
It was actually the last thing the Emperor wanted.
It was a moment of enormous potential
and latent threat to Byzantium.
Could they harness the power of these western hordes
or would they be overrun by them?
St Mary of the Mongols
is the only Byzantine church still operational in the city.
Historian Peter Frankopan took me there to understand what happened
when the westerners found themselves in the capital of eastern Christianity.
So when the first Crusaders arrive, how did it go, their first visit to Byzantium?
The first wave that arrives here behave like football hooligans
on tour who have had too much to drink,
so they steal lead off the roofs of the churches, they go berserk through the city
and riot police methods are put in place to make sure that the city stays safe.
They're quickly shunted off across the Bosphorus to keep them out of harm's way,
but even when they get there, they are said to impale children, to kill men, women
without asking whether they're Muslim or Greek or Christian
and they behave in a way that polite society in Constantinople just thinks is horrific.
Alexios, the Emperor at that time, who is the architect of the Crusades,
has real concerns that he's let a genie out of the bottle.
They are like country boys visiting a big, big city.
A traveller walks into Saint Sophia and he says, "I don't even know if I'm in Heaven or I'm on Earth."
There is a sense that the Orthodox are closer to early Christianity.
All the great relics of Christianity are here. All of the churches are older than anywhere else in Europe.
So this is what real Christianity looks and feels like.
That is a source of great admiration on the one hand, but also enormous envy on the other.
How did the relationship go from amazement and a bit of envy to wild hatred?
I think what happens is that the Crusaders and the Latin West get their claws into the Holy Land
and that requires a narrative that explains that they are the true heirs and defenders of Christianity.
At that point, all the animosities start to rise against the Greeks
and against the Orthodox clergy and against the Orthodox theology.
Small, little problems are suddenly blown up into major sticking points
and that poison starts to drip through into the west and it drips through very effectively,
so that the word "Byzantine" still today has very negative connotations.
Politicians are Byzantine, taxes and things that are bad are Byzantine,
so the Crusaders start as being Byzantium's allies at the moment of great weakness
and become their rivals and their nemesis.
History was taking an unexpected turn.
The fate of this city would finally be determined not by the battle with the Turks,
but by the battle with its own Christian allies.
Over the coming centuries,
wave after wave of crusading Latins stampeded through here
on their way to the Holy Land.
And more ominously still, others were coming to stay.
Parts of Constantinople were turning into a city within a city.
This area is called Galata and by the mid-12th century,
it was filled with new arrivals.
Not Crusaders, but merchants from Amalfi, Genoa and Venice.
It still has a distinctly Italian feel.
People here looked different.
They spoke different. They went to different churches.
The Latins were the new force in Constantinople.
But for the Byzantines, this was their world being turned upside down.
The Latins had once just been hairy axemen.
Now they were taking Byzantine jobs
and worming their way into its highest echelons -
the army, the government, the imperial family.
Something, they said, simply had to be done.
The people longed to be rid of the hated Latins
and for that, they needed a real Byzantine prince.
His name was Andronikos Komnenos.
And he was well known as the most glamorous and best-looking man in the entire Empire.
He was now 65,
but this silver fox had the looks, the energies and the appetites of a much younger man.
He was delighted to be crowned Emperor of Byzantium.
Xenophobic feeling was boiling against the Latins.
And in Andronikos, they had found just the kind of unscrupulous demagogue ready to use it
to his own advantage.
Andronikos unleashed the mob against the Latins
who were massacred to a man, their churches burned
and the Emperor's popularity surged on a tide of Latin blood.
As so often in history,
sectarian tensions had brought to power a self-serving autocrat
and ended in terrible violence.
Unfortunately for the Byzantines, they couldn't control the dark force they had unleashed.
Andronikos wasn't as charming as he looked.
The old swinger turned out to be a sadistic monster who launched a reign of terror.
He murdered his 13-year-old Co-Emperor
and then married his 12-year-old widow.
Even the Byzantines were appalled.
When the mob turned against him, he tried to run,
but he was captured and subjected to the most appalling torments.
First, his teeth were pulled out one by one,
then his hands were cut off and then he was skinned with boiling water.
Now they jeered, "You've really lost your looks."
The rise and fall of the tyrant Andronikos had scarred for ever
the holy streets of Byzantium.
Now murder and bloodshed was how this city solved its problems.
The ingredients for disaster were all coming together.
Byzantium was embroiled in an endless, internal power struggle.
The Latins and the Greeks were locked in a pitiless blood feud.
And the west had got a taste for the wealth of Constantinople.
It was a matter of time before all this resulted in cataclysm.
And that is the story of the Fourth Crusade.
It all had an unlikely start.
The Crusade's leader was one of the most extraordinary and sinister characters in this entire story.
He was the Doge of Venice, Enrico Dandolo,
and he was as forceful and ruthless as he was wily and avaricious.
Bald as a billiard ball and as blind as a bat,
he was already 80 years old,
yet still as sharp and predatory as an eagle.
And he had hated Constantinople for a very long time.
His hatred dated back to 1172.
The Byzantines took the side of Genoa
in its vendetta with Venice
and arrested every Venetian trader in the Empire.
Enrico Dandolo never forgave them.
The Crusading Army gathered in Venice.
They had the knights, but they needed ships to get to the Holy Land and only Dandolo had a fleet.
For that, he had a price
and the price was Constantinople.
The final ingredient was Alexius Angelus,
a Byzantine Pretender,
who offered the Crusaders the riches of Constantinople
in return for restoring him to his rightful throne.
In July 1203,
210 ships arrived outside Constantinople.
The Venetian fleet broke into the Golden Horn
and their sailors clambered up beams attached to the masts and on to the walls.
Dandolo directed operations from the prow of his ship, waving a banner,
and the blind, octogenarian Doge was one of the first ashore.
It was a moment of triumph for Dandolo,
but the beginning of the greatest disaster to befall Constantinople.
Behind these gates was once one of Byzantium's oldest and most venerated monasteries.
But I've had to get special permission to venture inside,
such is its dangerously dilapidated condition.
This is all that remains of St John Stoudios,
a monastery that was one of the holiest sites in Constantinople.
Its philosophers, its artists, its scholars were some of the greatest in Christendom
and it had a peerless collection of icons and manuscripts.
But by the end of 1204,
all of this was rubble and ashes.
The desecration of Byzantine Christianity took two years to unfold.
Golden, sacred icons, mosaics and candlesticks were ripped from their moorings,
first by the new Emperor's own agents,
and then when the Byzantines revolted, by the Crusaders themselves
in an all-out sack.
800 years of prayer by thousands of monks
was not enough to prevent sacrilege, murder and exile.
It was, some felt, as if God had abandoned them.
It's not only grand buildings that tell the story of this city.
This place is indelibly marked by that moment.
But nowhere escaped the rampage.
The Crusaders burst into the Church of San Sophia,
killing everybody they encountered, except the women.
These, they raped, especially the young virgins and the nuns.
They brought packhorses into the church and loaded them with treasures.
When the animals fell and broke their legs on the slippery human blood,
they disembowelled them right there and then, just for the hell of it.
Then the drunken knights held a homicidal orgy, inviting all the whores at the camp.
They crowned one lascivious strumpet on the Patriarch's throne
and there she danced half-naked
and sang bawdy songs.
These men had joined up to save Christendom from the Muslims.
Instead, they spent 50 years dividing up the spoils of Christianity's greatest city.
Like the pirates they were, the Crusaders took what they could from the city
and then began to look elsewhere.
They were away on a raiding party when Michael, the Greek Emperor in exile,
snuck back into the city.
The Crusaders didn't bother to fight over the ruin they had left behind.
Constantinople was once again the capital of the Roman Empire,
but that fatally wounded Empire was now little more than the battered city itself.
Constantinople in the 14th century AD,
a great world empire only in name,
its eastern territories in the hands of the Turks
and its lands in the west
overrun by the Latins,
and even its own port now outsourced to Italians from Genoa
who now overlooked Constantinople
from their tower in Galata.
Byzantium, once a city of half a million people,
was now a community of less than 50,000.
But still, they set about rebuilding the city
and against all odds, produced one last, extraordinary cultural flowering.
In the back streets of the Christian district Phanar,
one lonely church contains the last poignant remnants
of that defiant renaissance.
It's really exciting to be here.
These mosaics are simply awesome.
This is really like coming to the Sistine Chapel of Constantinople.
For 400 years, this was the Kariye Mosque
until, in the 1950s, they removed the whitewash and found this.
The Byzantine Church
of Saint Saviour in Chora.
These mosaics are part of its glorious 14th century restoration.
Here, for a moment,
God seemed to have returned to Byzantium.
What really strikes you about this masterpiece of Byzantine art
is the sheer beauty of the images.
The faces are very delicate, exquisite.
The reds, the blues, the greens are all still absolutely vivid
and, of course, the glory is the Byzantine gold.
This is often called the Byzantine Renaissance
because the Renaissance was just beginning to blossom in Italy at this time,
but actually, they're very different.
The Italian Renaissance was all about realism,
the celebration of the beautiful sensuality of the human body
that expressed God's perfection.
But the Byzantines didn't like that at all.
They regarded all that nudity as pornographic,
vulgar, disgusting.
For them, and you can see that when you look at these amazing images,
it was all about the celestial symbolism and the inner meaning,
the inner truth of their sanctity.
Each one of these pictures tells a story on a series of levels -
Biblical scenes laced with symbols of barely penetrable,
philosophical, mystical and political significance.
And in true Byzantine fashion,
the man behind all this reserved pride of place for himself.
This is one of the most famous images in Byzantine art
and it shows the founder of this church, Theodore Metochites,
presenting it to Jesus Christ.
Theodore was the Grand Logothete, the Imperial Prime Minister,
and the richest man in the Empire after the Emperor himself,
but he had a lot to live down.
His father had been a notorious collaborator with the Latins
and so, when he started on this project,
Theodore was saying, "Look at me, I'm not my father. I'm a real, true Byzantine."
And this is the quintessential Byzantine church.
All that mattered to Theodore was to be seen in the light of great Byzantines before him,
even though greatness now resided elsewhere.
This church stands testament to the Indian summer of a glorious culture,
turning its back on the changing world outside,
talking to itself in its own language of arcane and mystical symbols.
Even as the state was reduced to just the city itself,
even as enemy forces closed in from east and west,
Byzantium remained stubbornly and defiantly obsessed
with its own glorious past,
a doomed empire lost in introspection.
Constantinople was writing the last tragic chapter of its history.
The story that had begun a thousand years before with Constantine the Great,
the dream of a great Christian empire
and a great Christian city spanning Asia and Europe
was now at an end.
But the story of Istanbul was just beginning.
This is, after all,
a tale of THREE cities.
The history of this place looks completely different
from the Muslim perspective.
This is the heart of Muslim Istanbul,
the oldest mosque in the city, Eyup Sultan Camii.
It's named after one of the companions of Muhammad himself,
Ayyub al-Ansari,
who died and was buried here
when the first Muslims tried to conquer Constantinople
way back in the 7th century AD.
CHANTING OF PRAYER
This place isn't very well known in the west,
but here, it's enormously important
because it's the link between Islamic Istanbul and the prophet Muhammad himself.
The mosque is built around the tomb of Ayyub
and Ayyub was the prophet's companion in arms and standard-bearer.
And he died here in one of the first Arab Islamic sieges of Constantinople.
Twice, the followers of Muhammad besieged this city, for four years each time,
and for one reason above all.
The prophet himself had always predicted the Islamic conquest of Constantinople.
He said it would be a beautiful conquest by beautiful armies, by a beautiful conqueror.
And so this mosque has one central message to Muslims
that this city was always destined to fall to Islam.
But they would have to wait 700 years for that beautiful army and that beautiful conqueror.
They came in the end from a completely unexpected place
and that's the foundation myth of Turkish history.
IN TURKISH:
Yusuf Duru is one of the last meddah in Turkey,
storytellers who have passed on history, folklore and morality tales for generations.
Since the 1500s, men in this city have gathered during Ramadan
to hear about the great journey of their ancestors
into the lands we now call Turkey.
The foundation myth of modern Turkey rests on the shoulders of one man above all.
This is one of the great epic poems of Turkish history.
It tells the story of a 13th century Turkish chieftain named Osman
who ruled just a little bit of Anatolia.
Osman goes to see a holy man named Edebali
to ask for his daughter's hand in marriage.
Edebali says "no", but at this very moment, the moon emanates from Edebali's chest
and merges into Osman's chest.
And out of this fusion
grows a giant tree
whose branches overshadowed the great mountain ranges of the world, the Caucasus and the Balkans,
the great rivers, the Tigris, the Euphrates, the Danube, the Nile,
and these branches overshadow one great city -
Constantinople.
Osman and Edebali's daughter spawned a dynasty that ruled this city until 1922, the Ottomans.
Out of a small Anatolian principality,
Osman created an expansionist, warrior dynasty
and under his sons, grandsons and great-grandsons,
his domain grew into an empire.
By the mid-15th century,
the transcontinental Ottoman Empire dwarfed the Byzantine.
And it was closing in on Byzantium from every direction.
This is Anadoluhisari, the Anatolian Castle.
The Ottomans already possessed all of this - Anatolia
and far to the west in Europe, they had conquered the Balkans,
but this castle right here on the Bosphorus was as close as they'd got to Constantinople
when the throne was inherited by Sultan Mehmed II.
But he was just 19 years old and even his own ministers thought he wasn't up to the job.
But that teenager was none other than the man they call today Fatih the Conqueror,
the man who would put an end to Constantinople.
Mehmed was no mere callow teenager.
He was a supreme manipulator,
schooled in the cut-throat world of the Ottoman court and a brilliant military strategist.
He was also a sophisticated and cosmopolitan aesthete
who could read philosophy in Greek, Latin and Hebrew
and write passionate love poems to his concubine mistresses in courtly Persian.
When he was painted by the Italian Bellini,
the portrait shows his ferocious, delicate intelligence
and his boundless ambition.
He wanted to be the new Alexander the Great.
For Mehmed, there could only be one empire, the Ottoman,
one religion, Islam,
one emperor, himself,
and one capital, Constantinople.
Mehmed II was a greater figure than anyone suspected
and he set about the conquest of the world's greatest city
not with the recklessness of youth,
but with devastating and ruthless efficiency.
The Bosphorus is only 700 yards across here
and Mehmed's first bold move was to build a castle right on Byzantine territory.
And there it is - Rumelihisari, the castle on the Roman side.
But Mehmed had another name for it. The Throat Cutter.
It soon lived up to its name.
When an Italian Venetian ship, commanded by a Captain Rizzo, sailed along here,
Mehmed's castle told him to stop.
He defied it and ignored the warning.
They were blasted out of the water by Mehmed's cannons.
The entire crew were beheaded, except for poor Captain Rizzo,
who was impaled with a stake up his rectum
and left out here as a human scarecrow to warn Europe Mehmed II meant business.
The great confrontation that had been brewing for 400 years was finally at hand.
And the odds were stacked heavily in the Ottomans' favour.
Their ancestors had once been a gnat on the side of the Byzantine elephant.
Now Constantinople was just an enclave within the Ottoman Empire.
The last Byzantine emperor was named, fittingly,
Constantine.
As Mehmed II approached, Constantine asked for a summary of the city's defences.
When he heard the answer, he is said to have wept.
The Theodosian walls were still formidable,
but there weren't enough defenders to man them. They were a motley crew - adventurers, mavericks,
monks with crossbows, Venetian sailors, quixotic knights and an eccentric, John the German,
who was really from Scotland. The sort of desperadoes who fight in desperate wars.
There were only 5,000 of them against 200,000 Turks and the biggest cannons in Europe.
The Byzantines had no choice but to put their trust in the city's ancient physical defences,
which had seen off so many invaders before.
Constantinople's chief protection had always been the sea
and its most formidable maritime barrier still survives in the naval museum.
It's really amazing to actually see this famous piece of Constantinople's defence right here.
I'm quite excited.
When the city was in danger, this huge chain was winched up
from two towers on either side of the Golden Horn.
While it was up, no one could break through and besiege Constantinople on all four sides.
Now, in 1453, Mehmed II had to get past this in order to take the city
and he came up with a rather amazing solution.
What happened is the stuff of Istanbul legend.
A ghost that still haunts the contemporary city.
The site where Mehmed executed his most daring manoeuvre
is now the bustling heart of Istanbul.
This penthouse restaurant in Taksim Square is the best place to see what really happened
in the great Turkish siege of 1453.
Now if you look out here, you can see the city of Constantinople.
Mehmed had brought up his huge Turkish army to besiege the city,
but he could only besiege it from the land side.
Then he brought up his fleet, but he couldn't use it to enter that little channel over there.
That's the Golden Horn. He couldn't get in because the Byzantines had put the huge chain
right across this narrow channel there.
Mehmed was infuriated. He launched constant attacks. All of them failed.
He was so angry, he rode his horse into the sea in frustration
and threatened to execute his own admiral.
But then he came up with a great idea. He waited for nightfall
and when it came they laid rollers right across this piece of land here.
And thousands of slave and oxen, in an amazing feat of engineering,
moved his entire fleet from the Bosphorus there
all the way over here to the Golden Horn over there.
When the Byzantines awoke the next morning,
their most terrible nightmare had come true.
The entire Ottoman fleet was in the Golden Horn and they were surrounded on every side.
The last nights of Constantinople saw fervent prayer
and terrible omens.
God, they feared, was finally leaving His city.
The Ottoman guns pulverised the city for over a month.
And yet still the tenacious defence of the walls continued.
By dawn on the 29th of May, 1453,
the city walls had been under sustained bombardment by the Ottoman cannons for over a month.
Whenever they smashed a hole, the people of Constantinople worked night and day to repair the damage,
but now the Ottoman war cries of the huge army outside the walls told them one thing -
the final storm was coming.
The dying moments of the Byzantine city played out just near where I am standing.
One of Mehmed's big cannons finally brought down an entire section of wall.
He sent in assault after assault, first his irregulars, then his Bashi-Bazouks,
and, finally, the elite Janissaries.
After more than a millennium, the great walls of Byzantium had finally come tumbling down.
Without the protection of the walls, the outcome of the battle was a foregone conclusion.
The last bastion of classical antiquity had fallen.
Constantine XI, the namesake of the city's founder,
turned to his companions and said, "Come, men, let us fight the barbarians."
Then he threw himself into where the fighting was thickest.
The last of the Roman emperors was never seen again.
In this one place, on this one day,
the grinding tectonic plates of history seemed suddenly to shift.
The descendants of nomadic Steppe horsemen were now in possession
of the ancient capital of civilisation.
For Greeks, this is still the defining tragedy of their history.
Greek legend says that as the Turkish troops burst in to the church of San Sophia,
swords drawn, the priests conducting the last service
calmly turned and disappeared into the walls.
They will return when Constantinople is Christian again to continue the service.
The rest of the congregation were marched away to death or slavery.
But this was not to be the end for Hagia Sophia.
When Mehmed arrived to inspect the church of San Sophia,
he found one of his Turkish soldiers trying to prise marble off the floor.
He hit him with his sword, saying, "I gave you the treasure and the people,
"but the buildings are mine. From now on, the church of San Sophia will be the Great Mosque
"of Aya Sofya."
The 800-year-old prophecy of Muhammad had come true.
"Verily, you shall conquer Constantinople.
"What a beautiful leader will that leader be."
Mehmed II was now that promised leader.
The Crusaders had come here to pillage and destroy.
The Ottomans were here to fulfil the destiny of God's capital city.
To make it the capital of Islam.
CALL TO PRAYER
A new city was about to be born out of the ashes of Constantinople,
with the skyline and the soundtrack for which it is famed throughout the world.
The Ottomans brought with them the minarets that define Islamic architecture.
But the great domes were inspired by Hagia Sophia.
Because this is what the Muslims had come here for,
the thing that all this architecture stood for,
the Byzantine vision of a universal empire, blessed by God.
But their approach to Holy Empire was subtly different.
They replaced Byzantium's stifling orthodoxy
with a bewildering diversity of religious belief.
Ottoman Islam was infused with mysticism,
poetry, ancient spirituality.
This was the religion of the whirling dervish,
followers of the great poet of love, Rumi, who danced themselves into a trance of divine love.
Mehmed II was so open to un-Islamic ideas
that he sometimes shocked his own adherents.
He was seen once or twice in Istanbul's churches,
prompting outlandish rumours that he was about to convert to Christianity.
Mehmed II learned from the fate of Byzantium.
His empire would not shut itself off from outside influences.
He set about rebuilding this city on lines that were international and surprisingly inclusive.
After two centuries of war,
blockade and depopulation,
Istanbul's markets were once again thriving.
Sultan Mehmed followed a deliberate policy
of attracting to Istanbul and settling here peoples from all over the world,
regardless of their creed or nationality.
So from the east he attracted Christian Armenians,
Muslim Arabs, Kurds,
and from Western Europe he attracted Jews and Arabs
fleeing from the repressions of the intolerant Christians.
Not only that, but from the Balkans, Albanians, Greeks, Serbs, Bosnians.
And he succeeded, he and his successors, in making Istanbul the refuge of the world.
It's the culmination of a story heavy with irony.
The Emperor Constantine's great Christian capital had been brought to its knees
by the actions of Christians
and brought back to life by the vision of Muslims.
Thousands upon thousands had given their lives in the struggle,
but one character had emerged gloriously intact.
The city had suffered two centuries of disasters, culminating in total cataclysm.
But it wasn't the end. True, the Byzantine civilisation was all but destroyed,
but the city managed to beguile its new conquerors.
And their embellishments restored it to what it was always meant to have been -
the sacred, imperial capital of a faith and an empire.
The city of the world's desire.
Next time, I'm going to explore that Ottoman capital,
the creation of a legendary city,
from which larger-than-life emperors ruled as caliphs of Islam
until the end of the First World War.