Rome's power had already migrated; Constantinople simply made it permanent
Since Diocletian's era, Milan, Nicomedia, and Trier had already claimed Rome's authority and court; Constantine merely scaled up this existing practice of relocation, made it permanent, and put his own name on it.
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The site's real value was taxing merchant ships
Constantinople was built on a hilltop overlooking the strait connecting the Aegean and Black Seas, the Mediterranean and the Caucasus-Russian region. Every grain ship and merchant vessel had to pass this way. The location's actual strategic advantage wasn't the scenery or defensive benefits of water on two sides—it was the ability to assess, control, and levy taxes on every passing ship. This was what made Byzantium more valuable than neighboring Greek colonies; the defensive advantage was merely a bonus.
— Judith HerrinByzantium was an insignificant colony for a thousand years
Founded in the 7th century BCE by Megara settlers, Byzantium occupied the geography that would eventually let Constantinople dominate the Mediterranean. Yet for nearly a thousand years afterward it remained just a modestly prosperous small place. It produced no major scholars, no famous library, almost no historical record. Judith Herrin argues this absence of records reveals the truth: Byzantium had nothing remarkable to document. It neither monopolized the strait's trade nor rivaled Athens or Sparta in importance—just one of many ordinary Greek colonies. Its geographic advantage would take four more centuries to be fully realized.
— Judith HerrinRome's power had already left for other cities
Constantine's new capital is often presented as a sudden, visionary decision. But Rome's position as the empire's center had already eroded under Diocletian: Milan, better positioned to coordinate defenses on two fronts, became the actual power center. Nicomedia, Trier, Thessalonica, and Sirmium were all developed into palace-laden imperial capitals by different emperors. Rome itself had been controlled by the Senate too long; emperors relocated the court, judiciary, and administration to escape senatorial constraints. Constantine did not invent relocation—he only scaled it to unprecedented size and permanence, putting his own name on it.
— Judith HerrinConstantine tripled the city's area with new walls
According to Eusebius, Constantine's biographer and bishop, Constantine ordered the new walls drawn in ancient Greek tradition, using a plow. This line expanded the old Greek Byzantine city to 3 times its former area. Construction began in 324; six years later, in 330, the dedication ceremony took place—though many buildings were clearly rushed and not sturdy. The expanded space was used to plan the Milion (the zero point of all roads and distances, modeled on Rome's system), Constantine's Forum, and the imperial mausoleum that would rival Hadrian's Tomb. Constantine himself clearly invested more energy in these monuments to imperial power.
— Judith HerrinA stable coin gave Constantinople five centuries of trust
Constantine introduced the solidus, a gold coin minted to strict standard: 72 coins per pound of gold. This standard held until the mid-11th century—an achievement Judith Herrin says people often overlook. Because the purity was stable and trusted, Italian traders wore these coins as jewelry, Indian merchants in Sri Lanka used them for commerce, and they scattered across Scandinavia and Russia. They stood in sharp contrast to Western European silver coins that bent when you bit them. Currency trust itself became part of Constantinople's soft power.
— Judith HerrinSubway construction revealed 33 ancient shipwrecks
Two major harbors lined the Marmara coast south of Constantinople. One, the Theodosian harbor, was only discovered in the early 21st century—when subway construction required deep foundations at a junction of lines, workers found 33 intact shipwrecks in the mud, complete with cargo, vessels, and thousands of wine-stained amphorae. This harbor zone had been home to meat markets and grain storage (the largest granary was built on an island near the Dardanelles), sustaining a city now 3 times the size of old Byzantium.
— Judith HerrinRome's fall made Constantinople the empire's natural heir
When Rome fell around 410, Constantinople was positioned perfectly to inherit its role. Rome had been planned by Augustus and Aurelian to be so large that no garrison could defend all its gates and walls. Rival powers constantly sought its golden statues and jeweled treasures. Constantinople, by contrast, had resources enough—vast quantities of gold, silk robes, even entire bags of pepper—to simply buy off attackers. By 381, Constantinople was officially called the ‘New Rome’.
— Judith HerrinTheodosius's walls held invaders at bay for eight centuries
The three walls ordered by the young Theodosius II (with his powerful sister Pulcheria wielding real authority) in 413 massively expanded the city again. Towers stood every 50 meters along the walls, backed by a moat and outer fortifications in layers. This defensive system held all comers until 1204—and even then, the Venetians broke through the weaker sea walls rather than the landward ones. Real failure came in 1453 when cannon made them obsolete. Much of the land outside the walls was still vineyards and kitchen gardens then, but the expansion had swelled the population so much that Constantinople was now among the largest cities in the known world.
— Judith HerrinIn their own words · checked verbatim
It has the world in its hand, as if it was in some sense, a controlling factor in world history.
Judith Herrin4:08
A small place doing good business. And I think the fact that we know so little about it is partly because there was nothing very, very notable to record.
Judith Herrin11:44
It was like starting with a rather small acorn in order to grow a very big oak.
Judith Herrin22:30
There was monetary stability in the empire of Byzantium through to the mid-11th century, which is why they are collected and made into necklaces in Italy, and they're used in exchanges in Sri Lanka by Indian merchants.
Judith Herrin39:06
In the provinces of the Roman Empire, there was often silver pennies, but they bent in your teeth. If you chewed on them, you could bend them.
Judith Herrin40:06
The Venetians who knew about the fortifications could see that the sea walls were actually less strong than the land wall. And so they went over the sea defences rather than over the land walls, which remained until the great canon of 1453 blew them away.
Judith Herrin57:40
Figures
| Solidus gold-coin standard | 72 coins per pound of gold | 39:06 |
| City expansion under new walls | 3 times the old Byzantine city's area | 26:39 |
| Theodosian harbor shipwrecks discovered | 33 intact wrecks | 42:09 |
| Theodosius wall tower spacing | 1 tower every 50 meters | 56:38 |
| Solidus monetary stability | maintained through the mid-11th century | 39:06 |
| Walls finally breached | 1453 (by cannon fire) | 57:40 |
| Constantinople's administrative divisions | 14 districts (per Notitia) | 41:07 |
Glossary
- Tetrarchy
- Diocletian's system of dividing imperial power among four co-rulers
- Solidus
- Constantine's gold coin, standardized at 72 coins per pound of gold
- Milion
- Constantinople's zero-point marker from which all distances in the city were measured
- Notitia
- A fifth-century record documenting Constantinople's 14 administrative districts and structures
- Hippodrome
- The city's oval chariot-racing arena, situated adjacent to the imperial palace
How to listen
History enthusiasts interested in late Roman power shifts, urban site selection, and the origins of Byzantium.
Around 44:13, approximately one minute of garbled transcript repetition contains no actual content and can be skipped.