Attention: Due to construction of the Bosporus Rail Tunnel and new high-speed lines between Istanbul and Ankara all long-distance train services are suspended until 2015. Trains from Europe terminate at the border where designated buses are avalible for the rest of the journey. On the Asian side, trains from south (Konya and Adana amongst others) will have their terminus in Eskişehir. Trains from eastern Turkey and Iran terminates in Ankara. The sole exception of this are the trains from Gebze, a suburb 45km east of Istanbul.
International trains from across Europe arrive at the station in Sirkeci, close to Sultanahmet. Asian trains arrive at Haydarpasa station. To get between the two, catch a ferry across the Bosphorus. Marmaray, the Rail Tube Tunnel and Commuter Rail Mass Transit System is being built, and is projected to be one of the most challenging infrastructure projects in Turkey.
International trains to Sirkeci
Daily overnight train Balkan Express from Belgrade (Serbia) via Sofia (Bulgaria).
Daily overnight Bosphorus Express from Bucharest (Romania) (departure at 12:16PM from Bucharest, arrival at 8:30AM in Istanbul, but expect about 2 hours delay) Cost: 170 RON (about 40 euro) for a second class sleeper, plus an additional fee if you wish a sleeping compartment (77 euro for a single-bed cabin or 10 to 33 euro for twin/up to six beds/cabin). No restaurant.
Trains from Budapest and Thessaloniki are cancelled since 2011.
International trains to Haydarpasa
Schedule and price list of railway trips can be gathered from TCDD (Turkish Republic State Railways). Weekly trains to Aleppo (Syria) - taken out of service in 2008; it is unknown whether and when this service will resume.
Weekly train to Teheran (Iran) (from Haydarpasa station) every Wednesday 10:55PM, costing 105 Turkish lira. It is also a good way to drive in the Eastern part of Turkey. You change trains on Friday at Lake Van which requires a four hour ferry ride to get across. Both the Turkish and Iranian trains are comfortable and clean. Waggon restaurants are rather cheap. Arrival in Tehran on Saturday at 6:45PM (but expect up to 10 hours delay).
When arriving at the Turkish border from Europe, you may need to buy a visa before getting your passport stamp. This counter accepts only Euros or USD, not Turkish Lira. You need to go to the visa counter first to purchase your visa, then to passport control to get it stamped.