Travelling by bus
From Bucharest there is a daily bus to Istanbul at 16.00 for 125 Lei. There is also a daily bus from Constanta,Romania and from Sofia,Bulgaria and from there you can get connections to the major cities of Europe. Another possibility is the bus from Athens in Greece via Thessaloniki. You may also find smaller bus companies offering connections to other countries in the Balkans.
There is a direct bus to Istanbul from Teheran in Iran which takes approx 48hrs and costs US$ 35.00 for a one-way ticket between Istanbul or Ankara and Tehran.
From Aleppo in Syria a 3hr bus to Antakya costs S£250 departing at 5am. There is also a minibus service at 3pm for S£350. From Antakya you can get connecting buses to almost anywhere in Turkey, however initial prices may be overinflated and often inconvenient times. If travelling through to Istanbul, there are bus services from Damascus with bus changes along the way at Antakya. Purchasing a bus ticket in Damascus will be significantly cheaper than in Aleppo or Antakya. If traveling from Syria it is worthwhile to purchase additional supplies of snacks and drinks before leaving the country - these are significantly more expensive at bus stations in Turkey.