By Regional Coach
Regional coaches KTEL connect Athens to other cities in Greece. The fleet of buses has recently been upgraded, which makes the journey pleasant and safe. For some destinations one can also use the buses of the railroad company OSE, see next paragraph that might be international, but can also be used for in-country transport. At times there are collaborations with companies from adjacent countries such as Turkey, Bulgaria,Serbia, Macedonia and Albania, so your best move will always be to ask on both the bus and the train companies about your available options.
By train
The national rail service, Trainose, (http://www.trainose.gr) connects Athens to other cities in Greece -however, do not expect the diversity and complexity of railroads you usually find in other European countries; the national railroad system is poor in Greece, in effect having only two train lines. One goes south to the Pelopponese and the other to the north, connecting Athens with the second major city in Greece, Thessaloniki. From there the line continues further to the north and all the way to the east, passing through many other cities of northern Greece and eventually reaching Istanbul. Be advised that there are two kinds of train you can use; normal, slow, type of train equipped with beds, and the so called new 'Intercity' type which is more expensive because of a 'quality supplement fee' that grows with distance. For example, travelling from Athens to Thessaloniki by the 'Intercity' type will save you one hour at most, but the ticket will be almost double the price. 'Intercity' tends to be more reliable, yet more 'bumpy' than the normal train. There are no longer any international trains to and from Greece.