The Bosporus Strait gives Istanbul a unique place among world cities. The most important city in Turkey, Istanbul is the only city that stands on two continents — Europe and Asia. The Bosporus, which divides Istanbul, is about 35 kilometers long and connects the Black Sea in the north to the Sea of Marmara in the south. The European side of the city is the larger part and is itself divided by the Golden Horn, a tributary that empties into the Bosporus. Within the European section of the city are many of the city's historical monuments and buildings including Hagia Sophia (Ayasofya in Turkish), the Blue Mosque, the Mosque of Sultan Suleyman, the Topkapi Palace (now a museum), and the famous Kapal? Çarş? (pronounced "kah–PAH–luh CHAR–shuh") covered market.
Because of its strategic location, Istanbul was central to the region's trade routes, which linked Europe, Iran, the Arabian peninsula, the Horn of Africa, the Caucasus, the Russian steppe, the Balkans, and the Mediterranean Basin. The commercial republic of Venice was a major trading partner as well as a sometime rival and enemy. Ships sailed through the Black Sea and into the Mediterranean. Land routes stretched out toward Europe as well as along the Anatolian Plateau heading north, south, and east. Camel and horse caravans traversed the region. Istanbul's location made it a coveted city that armies often fought over.
Emperor Constantine I, ca. 280–337 C.E., a convert to Christianity, wrote in an edict that he established Constantinople as his capital "on the command of God." Called Byzantium when it was built in 667 B.C.E. by the Greeks, according to legend the city was founded by Byzas, the son of the Greek god Poseidon. All we know of legendary Byzas are images of his supposed likeness on Byzantine coins of later date. In 196 C.E. the city fell under Roman rule and was a pawn in ongoing power struggles between various Roman leaders until 330, when Constantine consolidated his power. Constantinople, the capital of what came to be called the Byzantine Empire or the Eastern Roman Empire, became the dominant city in Europe. Constantinople had a turbulent history as the capital came under attack by Persians, Arabs, Bulgars, Russians, and Venetians, among others. The city was occupied and plundered by Crusaders in 1204 but was retaken by the Byzantines in 1261. There followed more warfare, and in 1400 a Spanish traveler on his way to the court of Timur (Tamerlane), the Turkic leader in Samarkand, wrote, "Everywhere throughout the city there are many great palaces, churches, and monasteries, but most of them are now in ruins...." In 1402 Timur himself actually captured Constantinople for a brief period. In 1453 the city fell to the Ottoman Turk sultan Mehmet II.
"Ottoman" is the English name for the Osmanli Dynasty, named after Osman, the first leader of the Ottoman state. Every Ottoman ruler to the collapse of the Ottoman Empire in the 20th century was girded with the sword of Osman as part of his coronation ceremonies. Originally one of many small Turkish states that formed in Anatolia in the 14th century, the Ottomans conquered the Byzantine Empire in 1453, established their capital in the newly renamed city Istanbul, and moved on to conquer the rest of Anatolia and much of the Balkan Peninsula. Their conquest of Hungary brought the Ottomans into close contact with European states, and by the 16th century most of northern Africa and the eastern Mediterranean were also under Ottoman rule. In 1888 the first direct rail link between Western Europe and Istanbul was established when the Orient Express made its inaugural run.
The Ottoman Empire continued to control much of this territory until the 19th century. The empire was dissolved in 1918, and in 1922 the last sultan was overthrown by Turkish nationalists. From 1453 to 1922 the empire had been led by 36 rulers from a single family in direct succession. In 1923 the capital moved to Ankara, and in 1930 the city that, since 1453, had been called both Constantinople and Istanbul was officially given the sole, legal name of Istanbul.