There are several trains from Thessaloniki. Slow trains take 6h (9€), fast ICs take only 4 1/2h (16€).
Train connections are relatively frequent to the rest of the country, though the rail link to Bulgaria via Dikea has been canceled until further notice. Trains are running only to Dikea, 15km short of the Bulgarian border. There are no buses from Dikea to the border city of Svilengrad, with taxi and hitchhiking being the only options to access Svilengrad and the extensive Bulgarian rail network for the time being.
National Network of Buses or KTEL operates a frequent schedule of buses to all the major cities of the country. Shutle buses depart twice daily to Athens (approximately 8–9 hours) and there are hourly connections to Thessaloniki.
OSE, the national train operator, has set a daily bus shuttle to Istanbul that departs the main station early (around 7AM) every morning. Tickets are usually easy to find and can be booked in the ticket office.
Ferries to the island of Samothrace just to south of city leave mostly twice a day—but irregularly. There is a fast one (taking an hour and costing €17.70 pp), and a slower one also for cars (taking 3h and costing €8.80 pp). Tickets have to be bought in a travel agency near the port.
One of the reasons to visit Alexandroupolis is to take the train to the border station of Pythion and change to train to Istanbul there.