What is the farthest destination for the bus service in the city that does not currently have an intercity rail?
The Istanbul Metro comprises five lines (the M1, M2, M3 and M6 on the European side, and the M4 on the Asian side) with several other lines (such as the M5, M7, and M8) and extensions under construction. The two sides of Istanbul's metro are connected under the Bosphorus by the Marmaray tunnel, inaugurated in 2013 as the first rail connection between Thrace and Anatolia. Until then, buses provide transportation within and between the two halves of the city, accommodating 2.2 million passenger trips each day. The Metrobus, a form of bus rapid transit, crosses the Bosphorus Bridge, with dedicated lanes leading to its termini. İDO (Istanbul Seabuses) runs a combination of all-passenger ferries and car-and-passenger ferries to ports on both sides of the Bosphorus, as far north as the Black Sea. With additional destinations around the Sea of Marmara, İDO runs the largest municipal ferry operation in the world. The city's main cruise ship terminal is the Port of Istanbul in Karaköy, with a capacity of 10,000 passengers per hour. Most visitors enter Istanbul by air, but about half a million foreign tourists enter the city by sea each year.
International rail service from Istanbul launched in 1889, with a line between Bucharest and Istanbul's Sirkeci Terminal, which ultimately became famous as the eastern terminus of the Orient Express from Paris. Regular service to Bucharest and Thessaloniki continued until the early 2010s, when the former was interrupted for Marmaray construction and the latter was halted due to economic problems in Greece. After Istanbul's Haydarpaşa Terminal opened in 1908, it served as the western terminus of the Baghdad Railway and an extension of the Hejaz Railway; today, neither service is offered directly from Istanbul. Service to Ankara and other points across Turkey is normally offered by Turkish State Railways, but the construction of Marmaray and the Ankara-Istanbul high-speed line forced the station to close in 2012. New stations to replace both the Haydarpaşa and Sirkeci terminals, and connect the city's disjointed railway networks, are expected to open upon completion of the Marmaray project; until then, Istanbul is without intercity rail service. Private bus companies operate instead. Istanbul's main bus station is the largest in Europe, with a daily capacity of 15,000 buses and 600,000 passengers, serving destinations as distant as Frankfurt.
Frankfurt