Istanbul, Turkey is the fifth most populous city proper in the world behind Shanghai, Mumbai, Karachi, and Delhi. It is also one of the most historically significant cities in the world as it has been the capital of the Roman Empire, the Byzantine Empire, the Ottoman Empire and the Latin Empire under the names of Byzantium and Constantinople.
Istanbul can be reached by train, plane, bus, boat or car. Trains arrive from international cities around Europe and Asia. The European trains arrive into Sirkeci and the Asian trains into Haydarpasa. Ferries travel internationally as well. They arrive and depart at Karakoy Port. Busses arrive into Esenler Otogar (station). Although it is possible to drive into Istanbul it is not recommended as traffic is plentiful.
The main airport for Istanbul is the Atatürk International Airport (airport code IST), located just under 25 kilometres from the city centre. Atatürk International Airport is a hub for Turkish Airlines, Atlasjet and Onur Air.
Turkish Airlines flies to the most destinations out of the 86 airlines with flights from Atatürk International Airport. They also fly over 6,000 flights a year. The next most frequently flying airline is Lufthansa followed by United Airlines, SWISS and Egypt Air.