Roman and Byzantine Istanbul

The Byzantine era in Istanbul is considered to have begun in 300BC with Emperor Constantine the Great announcing the city as Byzantium and the capital of the Eastern Roman Empire, Istanbul’s unique and strategic position rendering the city favourable as a capital.
From that time on, the city came to be known as Constantinople, or the ‘city of Constantine’. It also came to be referred to as ‘New Rome’ due to its resemblance to that great western city. Both cities are spread across seven hills with the settlement of Old Istanbul confined by the Sea of Marmara and the Golden Horn, while those of Rome were established on either side of the River Tiber.
Shortly after the city became the capital, the power of Rome shifted eastwards and Constantinople became a centre for Christianity and Greek culture. During the reign of the Byzantine Empire the city was adorned with many artistic and architectural works. Roman temples were replaced by churches and many new churches, including the Hagia Sophia, which became the largest building in the world for a thousand years, were built in the four corners of the city.
During Constantine’s imperial rule the city witnessed great change and development with the hippodrome, aqueducts, city walls, palaces and squares being built. Towards the late Byzantine era Constantinople became the largest and wealthiest city in continental Europe.
The city became dilapidated after the Fourth Crusades, though 1261 marked a year of revival for the Byzantine Empire which had already been weakened greatly. The urban population decreased to just a hundred thousand from half a million as Byzantium lost its previous reputation as the strongest imperial power: the vast empire had shrunk so much that it now only occupied the area of Constantinople. Soon after the city became the target of the Ottomans and the Byzantine emperors accepted their hegemony and began to pay taxes to them. In mid-14th century the Ottomans began to capture small towns surrounding the city and shut down the supply routes that led to it.
Mehmet II spent a year preparing his attack on Constantinople. Molten metal was poured to make cannons and the Rumeli Fortress was built in order to bring the Bosphorus under their control as the number of soldiers was doubled. In April 1453 the first Ottoman advance troops appeared at the gates of Constantinople and after a siege of eight weeks, ships were hauled over land to the Golden Horn from Kasımpaşa. What was a shock for the Byzantines became a legend in the city’s history. Constantinople was seized by Sultan Mehmet II, who became known as Mehmet the Conqueror, and the city was announced as the new capital of the Ottoman Empire.

Source: How to Istanbul

Click here for a list of Byzantine and Roman monuments of Istanbul