The main destinations from Larissa Station are:Thessaloniki, Patra, Corinth, Alexandropouli, Kalambaka, Trikala, Karditsa, Katerini, Lamia, Livadia, Volos. The southern Peloponnese and western Central Greece are not served. It is apparently also possible to go by train to Nafplio in the Peloponnese with changing in Corinth, but the line is maybe under construction, so it is actually more sure to take the bus from Athens to go to Nafplio.Alexandropouli is the last town before the Greek Turkey border, it's there that you change train for Istanbul. Athens-Istanbul is approximately 20 hours of train, the ticket costs around 50 euros, you will need to change trains in Thessaloníki and at the Turkish border. You will need to be patient because 20 hours of train is a long process, especially when it is not possible to find a seat, as it is often the case between Athens and Thessaloniki. After Thessaloníki the ride is more comfortable, almost everyone got off the train, you can admire the beautiful scenery of northern Greece. The border crossing is a bit long, you will need to wait two hours in the middle of nowhere, and then to change train for a good old train until Istanbul.
For a cheap train to Thessaloníki, take the night train, which leaves at midnight from Athens, the ticket costs only 17 euros, be aware that it usually impossible to find a sit, not even to the corridor, it happened to me to be stuck 10 hours standing...
It is interesting to note that you can also go to the monasteries of Meteora by train, by stopping in Kalambaka, it is also the best solution to reach Kalambaka, the train is faster than the bus and cheaper. (11 euros).
Finally, you should know also that there are 3 types of trains, normal, Intercity and Intercity Express, the difference is in the convenience and the speed of the trains, prices vary considerably depending on the type of train, for example to Thessaloníki: a normal train is 17 euros. Intercity train: 35 euros. Intercity Express; 48 euros.
For more information, follow this link: www.ose.gr