Rail travel and trains in Greece
In Greece, the Greek Railways Organization, known in Greece by the initials OSE, operates the rail network. Though travelling by train in Greece is probably the cheapest form of transportation, it is also one of the slowest (apart from attempting to drive in Athens during the rush hour!!), if you travel by the trains that stop at all stations.
Situated within about 1km of each other in Athens near to the center around Omonias Square, you will find the 2 train stations, "Peloponnese" station and "Larisis" station. As is obvious from their names, the "Peloponnese" station is for trains to and from the Peloponnese only.
At the "Larisis" station, you will find trains for northern Greece, and stops in between. It is also here that you will find the international services, as well as the domestic ones.
Departing from "Larisis" station, you will find a daily train to Istanbul in Turkey, which travels via Thessaloniko and Alexandroupolis. Also traveling via Thessaloniki is a daily train to Sofia, Bulgaria. At Thessaloniki you will be able to take a train for your journey to Skopia.
There are also services to other parts of Europe, though these can be quite expensive, and it is probably more economical, as well as timesaving, if you use another form of transportation.