Archaeological remains show that people have inhabited the immediate area of present-day Istanbul for tens of thousands of years. A large population lived in the area around 5,000 B. C.

Greeks from Miletus and Megara began to settle along the coasts of Bosporus and the Black Sea during the latter part of the eighth century B. C. According to legend, the colony of Byzantium was founded in 660 B. C. by a Megarian named Byzas. The colony was named after him. Because of its strategic position, Byzantium didn't take long to establish its economic dominance over the region, inviting unwanted attention.

Byzantium was built along the Golden Horn, which provided the best natural harbor in the region. Fish were abundant, and the fertile surrounding countryside was suitable for agriculture. The Golden Horn inlet provided a safe harbor next to the city, not far from the Bosporus, a major maritime route connecting the Black Sea to the Mediterranean Sea.

Greeks, Athenians, Persians, and Spartans fought over the city early on. Even the Gauls attacked Byzantium in the third century B. C. In 202 B. C. Byzantium, besieged by Macedonians, asked Rome for protection. By 73 B. C. the city had become part of a Roman province.

In A. D. 196, Byzantium found itself on the wrong side of an internal Roman power struggle and paid dearly. Roman emperor Septimus Severus (146–211; r. 193–211) massacred its residents and destroyed most of the city. He rebuilt Byzantium, which continued to prosper despite serious attacks, civil wars, and rebellions that broke out in the Roman Empire over many decades.

On September 18, 324, Constantine I (c. 274–337; r. 306–337) defeated rival emperor Licinius and united the vast Roman Empire under his leadership. On May 11, 330, Byzantium officially became the capital of the empire, which stretched over three continents. Briefly known as New Rome, the city was renamed Constantinople in honor of Constantine, the first Roman ruler to adopt Christianity.

Constantinople became one of the world's wealthiest and most powerful cities of its time. Until the eleventh century, it was virtually untouchable, dictating Christian religious doctrine and controlling vast amounts of wealth. No longer did all roads lead to Rome. They led to Constantinople, the meeting point between East and West.

With the death of Theodosius in 395, the Roman Empire was split into East and West. Constantinople became the capital of the Eastern Roman Empire, which came to be known as the Byzantine Empire. The city developed into the center of the Greek Orthodox Christian world.

With vast amounts of wealth at its disposal, the Byzantine Empire transformed Constantinople into a beautiful city. Some of the best architects of the time designed its churches and palaces. Artists and sculptors left their mark

Istanbul rests on two continents, Asia and Europe, and is divided by the Bosporus Channel. Pictured is a view of the Golden Horn and the Bosporus towards Galata and Beyoglu areas, with the Yeni Mosque in the foreground. ()
throughout the city. The hippodrome could sit more than 100,000 people. The Haghia Sophia, today a museum, was one of the largest churches of its time. As the city grew, its nearly impenetrable protective walls were built further out.

During the reign of Byzantine emperor Justinian (527–565), more than 500,000 people lived in Constantinople. Justinian oversaw the construction of some of the city's most spectacular buildings, including the Haghia Sophia. Under his rule, the city reached its zenith.

The accumulation of wealth continued to attract enemies. In 542, a plague devastated the population, killing three out of five inhabitants, and marked the beginning of the city's decline. Its enemies besieged the weakened city but could not penetrate its walls. Between the seventh and eleventh centuries, Russians, Persian Sassanids, Avars, Muslim Arabs, and Bulgars attacked the city.

During the Fourth Crusade (a series of religious wars between Western European Christians and Muslims for control of the Holy Land), the Latins

Eating rooms were decorated with ornate tiles to entice the Sultan to eat. This is the fruit room from the Topkapi Palace. ()
(Roman Catholics) broke through the walls and seized the city in 1204.

They held it until 1261, when Byzantine troops recaptured the city. Under Latin rule, the city was plundered and ruined. The invaders stole most of the city's precious religious and civic symbols, melted its bronze statues for coin, and took just about anything of value that could be carried away. Constantinople would never recover from the destruction, even after the much smaller and weakened Byzantine Empire regained control. The city's population shrank to 50,000, and its people were constantly on the brink of famine. In the distance, the advancing troops of the Ottoman Empire moved closer and closer.

The Ottoman Turks attacked Constantinople for the first time in 1396. Ottoman is the Western derivative for the followers of Osman (1259–1326), a Sunni Muslim warrior who led raids on Christian Byzantine enclaves in western Anatolia (the Asian side of present-day Turkey).

The Ottomans built a fort on the Asian side of the Bosporus to prevent aid from reaching Constantinople. Yet the city would not fall for several decades. By 1452, under leader Mehmed II (r. 1451–1481), the Ottomans tightened the noose, building a second fortress on the European side of the Bosporus.

Mehmed commissioned the manufacture of large cannons to bombard the city's powerful walls. In March of 1453, Ottoman troops attacked the city by land and water. A massive chain prevented enemy ships from entering the Golden Horn. But Mehmed rolled his fleet by land on top of logs from the Bosporus into the Golden Horn. On May 29, Mehmed entered the city and prayed in the church of Haghia Sophia. It was a symbolic gesture that signaled the end of Constantinople's Christian era and the beginning of Muslim rule. The Haghia Sophia was immediately turned into a Muslim temple.

The city had been nearly abandoned during Mehmed's siege. He began to repopulate it by moving people into the city from other communities. In 1457, Constantinople, known by now as Istanbul, became the capital of the Ottoman Empire. Within a few years, the city was repopulated by more than 50,000 people.

During the rule of Suleyman the Magnificent (r. 1520–66), Ottoman Istanbul reached its zenith. The magnificent buildings of architect Mimar Sinan (c. 1489–1587) defined this period. As chief architect of the Ottoman Empire, Sinan is credited with more than 300 buildings. He designed palaces, mosques, tombs, and government buildings. With his buildings and the contributions of others, the city embraced a distinct Ottoman identity. For a while, it was the center of Islam.

By the nineteenth century, moderate sultans opened the doors to the West and sought better relations. Muslim Turks, Orthodox Greeks, Christians, Armenians, Jews, and many Europeans populated Istanbul. Yet, not all was well within the Ottoman Empire. Many non-Turkish people were in open revolt. The Greeks declared their independence in 1829, and soon others followed. The Europeans invested heavily in the Ottoman Empire. They openly sought to exert influence while secretly desiring the empire's territories and its wealth.

British, French, and Germans were involved in just about every aspect of Ottoman society. Foreign experts were reshaping the Ottoman Army and government administration with the approval of the ruling class. Sultans and government officials adopted the dress of Western diplomats, replacing their traditional clothes with Western pants and jackets. The fez replaced the turban. With European investment, Istanbul continued to modernize.

By the 1870s, Europeans were building a railroad to connect the continent with Istanbul. Modernization had come at a high price, and the empire was heavily indebted to European powers. In the meantime, many young Ottomans sought to limit the powers of the sultan and his western-style administration. The power struggles of the late nineteenth and early twentieth centuries would mark the end of the Ottoman Empire and the beginning of the Turkish Republic.

In 1908, a group known as the Young Turks forced Sultan Abd al-Hamid to restore the constitution and parliament. Al-Hamid attempted a counterrevolution in 1909, dissolving Congress and arresting many Young Turks. But allies of the young revolutionaries marched from Macedonia into Istanbul and dethroned the sultan. The Young Turks, who ruled until 1918, introduced many social changes, including Western-style elections and broader women's rights. During World War I (1914–18), the Ottomans aligned themselves with the Central Powers (the German and Austro-Hungarian empires). Istanbul was blockaded. At the end of the war, British, French, and Italian soldiers occupied Istanbul until 1923.

The nationalist Mustafa Kemal Atatürk (1881–1938) and his Turkish troops fought European intervention from 1918 until 1923 when hostilities ended with the Treaty of Lausanne. Atatürk abolished the sultanate and moved the capital city to Ankara. Turkey remained neutral during World War II (1939–45) and later became an ally of Western nations and member of the North Atlantic Treaty Organization (NATO).

During the twentieth century, Istanbul lost more than just its status as capital of empires. As it grew, large historic parts of the city were demolished to make space for highways and new buildings. Today, Istanbul struggles to retain its heritage as the portal between two worlds. Many of its buildings have been declared world heritage treasures by United Nations Educational, Scientific and Cultural Organization (UNESCO).