⛪ Eastern Rome and a thousand years of Constantinople — the empire whose monuments still define Istanbul.
Last reviewed on 3 June 2026.
The Byzantine Empire was the eastern continuation of the Roman Empire, centred on the city of Constantinople — modern Istanbul. For more than a thousand years, from roughly 330 to 1453, it carried forward the institutions, law and statecraft of ancient Rome while developing a distinctive Greek-speaking, Orthodox Christian civilisation of its own. To historians it is "Byzantine", after Byzantion, the old Greek colony on whose site Constantinople was built. Yet its own people never used that name. They called themselves Rhomaioi — Romans — and their state simply "the Empire of the Romans".
This continuity is key to understanding Byzantium. There was no single moment when the Roman Empire ended and a new Byzantine one began. The eastern half of the Roman world, richer and more urbanised than the west, gradually evolved: Latin gave way to Greek, Christianity replaced the old gods, and the centre of gravity shifted to the shores of the Bosphorus. The result was an empire that thought of itself as wholly Roman yet would have been scarcely recognisable to Augustus.
For Türkiye, the Byzantine millennium is not a foreign episode but a foundational layer of the country's past. The greatest Byzantine city stood where Istanbul stands today, and its walls, churches, cisterns and mosaics remain among the most visited monuments in the modern republic.
The story begins with Constantine the Great. In 330 he refounded the modest Greek city of Byzantion as a grand new imperial capital, naming it Constantinople — "the city of Constantine". Strategically placed on a defensible peninsula commanding the straits between Europe and Asia and between the Black Sea and the Mediterranean, it was conceived as a "New Rome", complete with its own senate, forums and hippodrome. Constantine also gave the empire a new religion: his patronage transformed Christianity from a persecuted faith into the favoured creed of the Roman state.
Through the fourth century the empire was repeatedly divided between co-emperors ruling east and west, a practical response to the difficulty of governing so vast a realm. After the death of Theodosius I in 395 the division became permanent, with one emperor in the west and another in the east. The two halves drifted apart in fortune as much as in administration.
Constantine the Great inaugurates his new capital on the site of Byzantion, establishing the city that would anchor the empire for over a thousand years.
On the death of Theodosius I, the Roman Empire is divided for the last time between his sons — Arcadius in the east, Honorius in the west.
The last western emperor, Romulus Augustulus, is deposed. The eastern empire endures, and Constantinople becomes the sole heir of Roman imperial authority.
The western empire crumbled under invasion and internal weakness during the fifth century. By 476, when the boy-emperor Romulus Augustulus was deposed, imperial government in the west had effectively dissolved. The east, however, survived. Wealthier, more populous and shielded by Constantinople's formidable defences, it absorbed the shock and carried the Roman name forward for another thousand years.
The sixth century brought the empire's most ambitious ruler, Justinian I (reigned 527–565). Determined to restore the old Roman world, Justinian launched a series of reconquests through his generals Belisarius and Narses. Imperial armies recovered North Africa from the Vandals, much of Italy from the Ostrogoths and a foothold in southern Spain. For a brief moment the Mediterranean was again, in part, a Roman sea — though these gains proved costly and largely temporary.
Justinian's most enduring achievements were not military. He ordered the codification of Roman law into a single authoritative collection, the Corpus Juris Civilis, which gathered, organised and clarified centuries of accumulated legislation. This body of law became the foundation of legal systems across Europe and remains one of the most influential legacies of the ancient world.
In architecture his monument was the Hagia Sophia, the great church of Holy Wisdom completed in 537 after an earlier church was destroyed in rioting. Its vast, seemingly weightless dome was an engineering marvel without parallel in its day, and for nearly a thousand years it was the largest enclosed space in the Christian world.
Justinian's reign was not untroubled. In 532 the Nika riots, sparked by factional rivalry at the Hippodrome, erupted into a full-scale revolt that nearly toppled him; tens of thousands were said to have died when imperial troops crushed the uprising. The empress Theodora, by tradition, persuaded the wavering emperor to stand firm. Less than a decade later, in 541, a devastating outbreak of plague — the Plague of Justinian — swept through Constantinople and the wider Mediterranean, killing a great part of the population and sapping the empire's strength for generations.
The centuries after Justinian tested the empire severely. It was locked in long, exhausting wars first with the Sasanian Persians and then, from the 630s, with the newly united armies of Islam. The Arab conquests stripped away Syria, Egypt and North Africa — the empire's richest provinces — within a single generation. Twice, in 674–678 and again in 717–718, Arab forces laid siege to Constantinople itself, and twice the great walls and the secret incendiary weapon known as "Greek fire" saved the city.
Internally the empire was convulsed by the iconoclast controversy, a bitter dispute over whether religious images, or icons, should be venerated or destroyed as idolatry. The quarrel raged through the eighth and ninth centuries before the veneration of icons was finally and permanently restored in 843, an event still commemorated in the Orthodox Church as the "Triumph of Orthodoxy".
To survive constant warfare, the empire reorganised its provinces into military districts called themes, where soldiers held land in return for service — a system that gave Byzantium a resilient defensive structure for centuries.
Under the Macedonian dynasty (867–1056) the empire enjoyed a revival of power and culture, reconquering lost territory and witnessing a flowering of art, scholarship and learning that drew on classical models.
In 1054 long-simmering disputes over doctrine and papal authority led to a formal breach between the Orthodox Church of Constantinople and the Latin Church of Rome — a division that endures to this day.
By the early eleventh century, under emperors such as Basil II, the empire had recovered much of its strength, securing the Balkans and pushing its frontiers eastward. Yet the rift with the Latin West, formalised in the Great Schism of 1054, would have grave consequences in the centuries to come, poisoning relations between Byzantium and the Catholic powers of Europe.
At its height Constantinople was the largest and richest Christian city of its age, a wonder that astonished travellers from across the known world. Its defences were the most formidable ever built: the Theodosian land walls, completed in the early fifth century, were a triple line of walls, towers and a moat that protected the city's landward side and repelled besieger after besieger for a thousand years.
Within the walls rose the great monuments of empire. The Hagia Sophia dominated the skyline; the Hippodrome, a vast chariot-racing arena adapted from the Roman circus, was the focus of public life and political passion; and palaces, churches and monasteries glittered with mosaics and icons in gold and coloured glass. The city's markets traded in silk, spices and goods from three continents.
For medieval visitors, Constantinople was simply "the City" — so pre-eminent that no further name was needed. Its population, perhaps approaching half a million at its peak, dwarfed any city in western Europe. Its relics, its art and its sheer wealth made it the envy of friend and foe alike, and the awe it inspired would ultimately help to bring about its undoing, drawing the covetous gaze of crusaders and conquerors. The Greek phrase for travelling there, "eis tin polin" — "to the city" — is widely thought to lie behind the later name Istanbul.
This concentration of beauty and treasure made Constantinople not only the political heart of the empire but also its spiritual and artistic centre, a living showcase of Byzantine civilisation that shaped the Orthodox world far beyond the empire's borders.
The turning point came in 1071. At the Battle of Manzikert in eastern Anatolia, the Seljuk Turks defeated and captured the emperor Romanos IV Diogenes. The defeat itself was not catastrophic, but it shattered the empire's eastern defences amid the civil strife that followed, and over the next decades the Seljuk Turks overran most of inland Anatolia — the empire's chief recruiting ground and granary. Byzantium would never fully recover this heartland.
The Seljuk Turks defeat the Byzantine army and capture the emperor, opening the way for the loss of inland Anatolia.
Byzantine appeals for help against the Turks helped spark the Crusades, bringing western armies through imperial lands — allies who too often became rivals.
The Fourth Crusade, diverted from the Holy Land, storms and pillages Constantinople, dividing the empire among Latin lords.
Seeking aid against the Turks, the emperors turned to the West, and their appeals helped set the Crusades in motion. But the relationship between Byzantium and the crusading powers was fraught with mistrust. It ended in disaster in 1204, when the Fourth Crusade — diverted from its goal of the Holy Land — turned on Constantinople itself, storming the city and subjecting it to days of looting that stripped its churches of relics and its palaces of treasure. The empire was carved up among Latin rulers, and a Latin emperor sat on the throne for more than half a century.
Byzantine successor states kept the flame alive, and in 1261 the rulers of the Empire of Nicaea recaptured Constantinople and restored the empire. But the restored state was a shadow of its former self — territorially diminished, financially exhausted and increasingly hemmed in by rising powers, both the Latin states and the advancing Turks.
Through the fourteenth and early fifteenth centuries the empire shrank steadily until it amounted to little more than the capital and a few scattered territories. The Ottoman Turks rose around it, conquering its remaining lands and surrounding the city on every side. By the mid-fifteenth century Constantinople was an island of Byzantium in an Ottoman sea.
The end came in 1453. The young Ottoman sultan Mehmed II, later called "the Conqueror", laid siege to the city in the spring of that year with a vast army and powerful cannon, including a giant bombard capable of breaching even the Theodosian walls. After weeks of bombardment and assault, the defences were broken on 29 May 1453. The last Byzantine emperor, Constantine XI Palaiologos, died fighting in the final hours, and the City fell at last.
The fall of Constantinople closed the long history of the Byzantine Empire and opened a new era. The city became the capital of the Ottoman Empire, and the Hagia Sophia was converted into a mosque. The conquest reverberated across Europe and is often taken to mark the end of the Middle Ages.
Though the empire perished, its influence did not. Byzantium had been the great bastion of Orthodox Christianity, and through its missionaries and its art it had carried that faith to the Slavic peoples of the Balkans and Russia. Long after Constantinople fell, the Orthodox tradition it had nurtured continued to shape the religious life of much of eastern Europe.
The empire was also a vital guardian of the classical past. Byzantine scholars copied, studied and preserved the literature, philosophy and science of ancient Greece and Rome through centuries when much of it was lost in the West. When Byzantine refugees and manuscripts reached Italy in the empire's final years, they helped to fuel the Renaissance. Roman law, codified under Justinian, remained a cornerstone of European legal thought.
Byzantium shaped Orthodox Christianity and spread it across the Balkans and the Slavic world, leaving a religious legacy that endures across eastern Europe.
The empire preserved the literature and learning of ancient Greece and Rome, and its scholars helped ignite the Renaissance in the West.
Justinian's codification of Roman law became a foundation of legal systems across Europe and beyond.
In Türkiye, the most tangible legacy is architectural. The Hagia Sophia still crowns the old city of Istanbul; the Chora church, the Kariye, preserves some of the finest late-Byzantine mosaics and frescoes in existence; and the great underground cisterns, such as the Basilica Cistern, still draw visitors beneath the streets. Stretches of the Theodosian walls survive, as do many churches and chapels woven into the fabric of the modern city. These monuments make Istanbul one of the world's great open-air museums of Byzantine civilisation.
The Byzantine Empire was the eastern continuation of the Roman Empire, centred on Constantinople (modern Istanbul) from roughly 330 to 1453. It was Greek-speaking and Orthodox Christian, yet its people always considered themselves Romans and called their state the Empire of the Romans.
There was no clean break between them — "Byzantine" is a label coined by later historians for the eastern Roman Empire after the western half fell in 476. The eastern empire gradually became Greek-speaking and Christian rather than Latin and pagan, but it saw itself, without interruption, as the Roman Empire continuing on.
Constantinople commanded the straits linking Europe and Asia and the Black Sea and the Mediterranean, making it a hub of trade and a superb defensive position. Protected by the mighty Theodosian walls, it was the largest and richest Christian city of its age and the political, religious and cultural heart of the empire for over a thousand years.
The empire fell on 29 May 1453, when the Ottoman sultan Mehmed II captured Constantinople after a lengthy siege. The last emperor, Constantine XI, died in the fighting, ending more than a thousand years of Byzantine rule.
Istanbul preserves some of the finest Byzantine monuments anywhere, above all the Hagia Sophia. Visitors can also see the mosaics of the Chora church (the Kariye), the underground Basilica Cistern and other cisterns, and surviving sections of the Theodosian land walls.
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