During the 4th century, Istanbul was selected by the Roman Empire to be the new capital, instead of Rome, by Constantine. It was a strategic choice: Built on seven surrounding hills – echoing that of Rome – the city would have control of the Bosphorus and easy access to the harbour of the Golden Horn. The city was re-organized within six years, its ramparts widened and the construction of many temples, official buildings, palaces, hamams and hippodrome.

With great ceremony, in the year 330 the city was officially announced as the capital of the Roman Empire, and known as Constantinople in the late eras. It remained the capital of the eastern Roman Empire (Byzantine) for a long period, due to the fall of the west Roman Empire in the 5th century. By the sixth century, the population exceeded half a million, and was considered a golden age under Emperor Justinyen’s reign.

The Byzantium Empire and Istanbul's latter history is full of palace and church intrigues, was overrun by the Arabs in the 7th and 8th centuries, the Bulgars in the 9th and 10th, but could not keep out the Crusaders who conquered in 1204. They destroyed and raided it for many more years - including churches, monasteries and monuments, which led to a decline in the population. The city passed reign to Byzantium again in 1261, did not regain its former richness, and was conquered by Turks in 1453 after a 53-day siege and the hands of control changed yet again.

It then became the capital city of Ottoman Empire, which saw a population increase with immigrants from other parts of the country, with religious freedom and social rights granted to Greeks, Armenians and Jews. Mehmet the Conqueror began to rebuild it, with a new palace and mosque (Fatih Camii) and tried to inject new life into the economy.

The reign of Suleyman the Magnificent (1520-66) was considered the greatest of all the Ottoman leaders, and the military conquests paid for the most impressive Ottoman architecture, the work of Mimar Sinan. The city was also the centre of the Islamic work, and domes and minarets from hundreds of mosques dotted the skyline.

But a century after the death of Suleyman, the Empire started to decline again. By the end of the 18th century the empire was in decline with more territory being lost to the West, and sultans becoming more interested in Western institutional models. There was a short-lived Ottoman parliament and constitution in 1876, and by the end of the World War I during which allied troops occupied the city, the once-great empire was in shambles.

This changed radically with the emergence of a prominent commander of the Turkish army, who entered the struggle for the Turkish nation. Mustafa Kemal Ataturk was considered a hero after the 4-year long War of Independence, after which he established the Republic if Turkey in 1923. Moving the capital to Ankara, then a small provincial town in Anatolia, Istanbul was simply the commercial and cultural centre, which it still remains today.