Istanbul Before Constantinople: The City That Was Byzantium

Short answer first: before it was Constantinople, this city was Byzantium, a Greek colony founded around 660 BC. And before even that, a couple of small fishing settlements with the names Lygos and Semistra sat on the same headland. So the city most of us picture as a thousand-year Byzantine capital actually spent its first thousand years as something much smaller and more Greek, perched on a peninsula that everyone with a fleet wanted to control.

I find this part of the story more interesting than the famous Constantinople chapter, honestly. The reason the place mattered was never an accident. It sits where Europe and Asia almost touch, on a narrow strait connecting the Black Sea to the Mediterranean, with one of the finest natural harbors in the region tucked along one side. Whoever held this rock controlled who passed through, and that single fact pulled in Thracians, Greeks, Persians, Romans, Byzantines and Ottomans in turn. If you want the long version across every era, our full history of Istanbul covers it, but here we are going to stay before 330 AD.

• Istanbul Before Constantinople Overview
• Istanbul During the Eastern Roman Empire Period: Constantinople
• Istanbul After Constantinople: Kostantiniyye
• What Was Istanbul Before Constantinople Like?
• Which Civilization Had Istanbul Before Constantinople?
• When Did Constantinople Become Istanbul?
• Istanbul Today
• Final Words

Istanbul Before Constantinople Overview

Here is the whole timeline in one breath, because the names get confusing fast.

The oldest layer is two small fishing villages, Lygos and Semistra, on the tip of the peninsula now called Seraglio Point. Around 660 BC, Greek colonists from Megara built a proper city there and called it Byzantium, after their leader Byzas. Byzantium stayed a Greek city for centuries, then passed to Rome. In 330 AD the emperor Constantine refounded it as his new capital and it became Constantinople. Under the Ottomans, who took it in 1453, the official name was Kostantiniyye (just the Ottoman Turkish form of Constantinople), though locals already used Istanbul. The Turkish Republic made Istanbul the only official name in 1930.

So the order is simple: Lygos, then Byzantium, then Constantinople, then Kostantiniyye, then Istanbul. Five names, one peninsula. The rest of this post fills in the people and dates behind each step.

Istanbul During the Eastern Roman Empire Period: Constantinople

Before we get to the Byzantium years, it helps to set the bookend, the moment the city stopped being a regular provincial town and became the most important place in the Roman world.

By the 1st century, Byzantium had been absorbed into the Roman Empire. Then it made a costly political bet. In the civil war after Emperor Commodus, the city backed Pescennius Niger against Septimius Severus, and it lost. Severus besieged Byzantium for roughly two years, from 195 to 196 AD, and when it finally fell he tore the walls down to the ground, executed officials and soldiers, and stripped the place of its status. Not long after, the same emperor changed his mind and rebuilt it, adding new walls, a forum, and the first version of the Hippodrome. That Severan rebuild is a big part of why the city was ready, a century later, to become something far grander.

The far grander thing arrived with Constantine. He became sole emperor in 324 and went looking for a new capital that suited a Christian, eastern-facing empire. He chose Byzantium, and on 11 May 330 he formally dedicated it as Nova Roma, “New Rome.” The name that actually stuck was Constantinople, the city of Constantine. When the Roman Empire later split for good into western and eastern halves, Constantinople became the capital of the Eastern Roman (Byzantine) Empire and held that role for more than a thousand years. The defensive system that kept it safe through countless sieges, the famous Walls of Constantinople, still rings the old city today, and the church Justinian raised in the 530s, Hagia Sophia, is still standing.

Also read: Why is Istanbul not Constantinople?

Istanbul After Constantinople: Kostantiniyye

I know the section title sounds backwards, but stay with me. To understand “before,” it helps to see “after,” because the after part is where most people’s mental image of this city lives.

In 1453, Mehmed II and the Ottomans took the city, ending the Byzantine Empire. Under Ottoman rule the official name became Kostantiniyye, the Ottoman Turkish version of Constantinople, although Istanbul was already in everyday use (it most likely comes from a Greek phrase meaning “to the city”). Kostantiniyye served as the Ottoman capital from 1453 until 1922, and it stayed a wealthy hub of trade, faith and craft the whole time. If you want to walk through that chapter rather than read about it, the Ottoman historical places in Istanbul are still scattered all over the city, from imperial mosques to the great covered bazaars.

What Was Istanbul Before Constantinople Like?

Now the real question. Before Constantinople, the city was Byzantium, and the founding story is a good one.

Greek colonists from Megara sailed out looking for a new home around the middle of the 7th century BC. The traditional date you will see most often is 667 BC, though some sources put it a few years later, around 657 or 660 BC. Their leader was Byzas, which is where Byzantium gets its name. The legend says Byzas asked the Oracle at Delphi where to settle, and the oracle told him to build “opposite the blind.” When he reached the strait, he saw an existing Greek colony, Chalcedon, sitting on the Asian shore, and realized its founders had been “blind” to choose that side while ignoring the magnificent harbor and defensible peninsula directly across the water. So he settled on the European point instead. That harbor, by the way, is the Golden Horn, and the strait is the Bosphorus that still defines the city.

The Greeks were not the first ones here, though. Two small fishing settlements, Lygos and Semistra, already occupied the headland we now call Seraglio Point, the same green spit of land where Topkapı Palace would later stand. Lygos is usually described as a Thracian settlement, which makes the Thracians the oldest named inhabitants of the site.

Byzantium itself had a rough ride before Rome. The Persians held it for a stretch during their wars with the Greek world, then the Greeks took it back. It joined the Delian League and later the Second Athenian League, won its independence around 355 BC, and stayed a self-governing trading city for a few more centuries until Rome absorbed it in the 1st century BC. Through all of it the draw was the same: tolls, grain ships from the Black Sea, and a harbor you could chain shut against enemy fleets.

Which Civilization Had Istanbul Before Constantinople?

Reading the timeline backwards from 330 AD, the city changed hands like this.

Right before it became Constantinople, it was Roman, a provincial city of the Roman Empire. Before Rome, it was an independent Greek city named Byzantium, one that spent time inside the Delian and Second Athenian Leagues and a brief spell under Persian control. Before the Greeks founded Byzantium, the site held the Thracian fishing village of Lygos (and its neighbor Semistra). So the honest answer to “which civilization” is that it was several in sequence: Thracians, then Greeks, then Romans, each building on what the last left behind, long before a single Byzantine emperor sat on a throne here.

When Did Constantinople Become Istanbul?

The name Istanbul became official in 1930, but the story behind it starts earlier.

The Ottoman Empire spent its final century in decline, the so-called “sick man of Europe.” It joined World War I on the losing side, was occupied and partitioned, and that pressure helped trigger the Turkish War of Independence. Out of that war came the Republic of Turkey in 1923, with Ankara, not this city, chosen as the new capital.

As part of distancing the young republic from the Ottoman past, the old names were dropped. Kostantiniyye and Constantinople fell out of official use, and in 1930 the Turkish Post Office formalized Istanbul as the single name, asking foreign senders to use it too. So Constantinople did not “become” Istanbul in one dramatic instant. The name had been in local use for centuries and was simply made official in the republican era.

Also Read: 10 Amazing Ottoman Historical Places in Istanbul to See

Istanbul Today

Stand on that same peninsula now and the contrast is almost funny. The fishing village of Lygos has turned into one of the largest cities on earth.

Istanbul’s population sits around 16 million at the time of writing, which makes it bigger than several European countries on its own. It generates the largest share of Turkey’s economy by a wide margin, and it draws an enormous number of visitors, somewhere in the range of 18 to 19 million foreign tourists a year in recent counts, with projections nudging toward 20 million. People come for the obvious reasons: a skyline of imperial mosques and Byzantine domes, a working strait you can cross by ferry in minutes, food worth flying for, and beaches and forests within the city limits if you go looking.

What I love is that all five historical layers are still legible if you know where to look. The harbor Byzas chose, the walls Theodosius raised, the church Justinian built, the palace the Ottomans ran an empire from, and the bridges and metros of the modern city all share one peninsula. You can walk from Byzantium to today in an afternoon.

Final Words

So, what was Istanbul before Constantinople? It was Byzantium, the Greek city founded by Byzas of Megara around 660 BC on a strait everyone wanted to control. And before Byzantium it was Lygos, a small Thracian fishing settlement on the same point of land. The Greeks turned it into a trading power, the Romans absorbed it and (after Septimius Severus nearly leveled it) rebuilt it, and Constantine refounded it as his New Rome on 11 May 330, the moment Byzantium became Constantinople.

The deeper point is consistency. For roughly 2,700 years, the reason this place kept mattering never really changed. The geography did the work, and the names just kept catching up to it. If the ancient end of the story pulled you in, Constantinople on Wikipedia is a solid deep dive, and the closely related question of why Istanbul is not Constantinople picks up exactly where this post leaves off.