Istanbul History: A Look At The Past Of This Great City

Here is the short version, in case you only have a minute: Istanbul is roughly 2,700 years old, it has been the capital of two of the largest empires the world has seen, and it is the only major city that sits on two continents at once. Greek colonists started it as Byzantion around 660 BC. The Romans renamed it Constantinople in 330 AD. The Ottomans took it in 1453 and ruled from it for nearly five centuries. That is a lot of history packed into one peninsula, and you can still touch most of it on foot.

I think knowing even a little of this makes the city land differently when you arrive. The walls you walk past, the domes you photograph, the hill you climb for a sunset, all of them sit on layers of older stories. So before you start ticking off things to do in Istanbul, let me walk you through the timeline, then explain why this particular spot of land mattered so much for so long.

A Short Istanbul History Timeline

The thread that runs through all of it is location. The city guards the Bosphorus, the narrow strait where Europe and Asia almost touch and where the Black Sea funnels down toward the Mediterranean. Whoever held this point controlled trade between two continents and two seas. That is why empire after empire fought for it, and why it kept reinventing itself instead of fading away.

Prehistory And Ancient Times

People lived here long before anyone wrote it down. Excavations near Yenikapı, dug up during the Marmaray rail tunnel project, turned up traces of settlement going back roughly 8,000 years, plus a Byzantine-era harbor full of shipwrecks. So the area was inhabited well before the Greeks arrived.

The city we can actually name starts around 660 BC. Settlers from Megara, a town near Athens, founded a colony on the European side of the strait and called it Byzantion, after their leader Byzas. An earlier settlement called Lygos may have stood nearby. What the Megarians had spotted was the Golden Horn, a deep natural harbor that made the place an obvious trading port. If you want the full story of those first centuries, I put it in Istanbul before Constantinople.

Roman And Byzantine Empires

Rome absorbed Byzantion in 196 BC. The city took heavy damage in a siege under Emperor Septimius Severus, then got rebuilt. For a while it was just another provincial town living in Rome’s shadow.

That changed in 330 AD. Emperor Constantine the Great moved the capital of the Roman Empire here and renamed it Constantinople, partly because the site was easy to defend and sat right on the trade routes between Asia and Europe. When the empire later split, this became the heart of the Eastern Roman, or Byzantine, world. Under Justinian I in the 6th century the population pushed toward half a million, making it the largest city in the West. Justinian also built the Hagia Sophia, finished in 537, which held the record as the world’s largest cathedral for almost a thousand years.

The other survivor from this era is the wall. The Theodosian Walls, completed in the early 5th century, ringed the land approach to the city and shrugged off siege after siege for a thousand years. You can still walk long stretches of them, and I cover the route in my guide to the Walls of Constantinople.

The Ottoman Conquest Of 1453

The walls finally met something they could not handle: gunpowder. In the spring of 1453 the young Ottoman sultan Mehmed II surrounded the city with somewhere around 80,000 troops, against maybe 7,000 to 10,000 defenders. His real advantage was artillery. The largest cannon was about eight meters long and could throw a stone ball weighing over 250 kilograms, and it took teams of oxen and hundreds of men just to move it.

The siege ran about 53 days. For the first time in history, the Theodosian Walls were being battered faster than the defenders could patch them. On 29 May 1453 the city fell, the last Byzantine emperor died in the fighting, and Constantinople became the capital of the Ottoman Empire. Mehmed, now called “the Conqueror,” turned Hagia Sophia into a mosque and set about rebuilding the city he had just taken.

Ottoman Capital To Turkish Republic

Under the Ottomans the city had its second golden age. Sultan Süleyman the Magnificent and his architect Sinan filled the skyline with the domes and minarets you still see today, including the Süleymaniye Mosque. The sultans ruled from Topkapı Palace for centuries before moving to the more European Dolmabahçe Palace on the water in the 1850s.

Then the empire ended. After the First World War and the Turkish War of Independence, the Republic of Turkey was founded in 1923, and on 13 October 1923 the capital moved to Ankara, deeper in Anatolia and safer from the coast. The city we are talking about lost its political crown but kept its commercial one. The name was the last piece to change: on 28 March 1930 it officially became Istanbul, and foreign post offices were told to stop delivering mail addressed to “Constantinople.” If that switch interests you, I dug into the why in why Istanbul is not Constantinople.

Why Was Istanbul So Important In History?

In one word: geography. The city sits on the Bosphorus, the only sea route between the Black Sea and the Mediterranean, and on the land bridge between Europe and Asia. So it controlled trade in both directions, by ship and by road. Anyone moving silk, grain, or armies between the two continents had to deal with whoever held this strait. The importance of the Bosphorus really is the whole story in miniature.

The same water that made it rich also made it hard to attack. The sea protected three sides, the great walls protected the fourth, and the Golden Horn gave it a sheltered harbor that could be sealed off with a chain in wartime. Rich, defensible, and standing at the crossroads of the known world: no wonder every empire in the neighborhood wanted it. For a wider look at what still pulls travelers in, see why Istanbul is so famous.

How To See This History Yourself

The best part is that almost all of it is still standing, and a lot of it sits within walking distance in the old Sultanahmet peninsula. Hagia Sophia and the Blue Mosque face each other across a square, with Topkapı Palace a short stroll away and the Basilica Cistern underground nearby.

A quick, honest note on Hagia Sophia, since it is the building everyone asks about. It returned to use as a mosque in 2020, and as of the time of writing in 2026, foreign visitors pay around 25 euros for the upper-gallery “Visiting Area,” where the famous mosaics and views are. The ground floor stays free but is reserved for worship, it closes to tourists during the five daily prayers (the longest gap is around Friday noon), and you will want shoulders and knees covered, with a headscarf for women. Go early in the day if you can.

If you would rather have all this explained out loud as you walk, a free walking tour of the old city is a great first morning. Two and a half millennia of empires, all on one peninsula, and you can cover the highlights of it before lunch.