Taking a Bike on a Train in Greece
I spent a long time trying to find out how to take a bike on a train in Greece, but the information I found was out-dated, sparse and contradictory. So I thought I would post details that will be of use to others.
First of all, I think there may be some lines that may not allow bikes at all, but you would have to check. But the main lines, like Thessanoliki to Athens, do. However bikes are not always accepted. The best way to find out if a bike is accepted is to go to the information desk and ask. It appears to be peak-hours trains that do not accept bikes - those travelling at around 8 AM and 5 PM.
I took the 10AM train from Thessanoliki to Athens, though I got off at a small stop. On arriving at Thessanoliki Railway Station, I took my bike to the luggage check-in, where a man who did not speak English gave me a label to put on it and a piece of paper. You then carry your bike to the platform and wait for the train. The baggage car will be at the front of the train. Someone will come along and take your bike and place it in a small room. If you have a bike lock, you can lock your bike to the railings in there. This is a locked room, both on the outside and inside of the train.
When you are approaching your destination, travel down to the car that holds the luggage and there should be some train staff there. Show them your piece of paper and when you get close to the station they will open the room where your bike is held. Once you arrive at the station, you will need to get out of a carriage that is probably 60-70cm from the ground. You will need to take your piece of paper to the ticket office to tell them your bike has been picked up. In my case, the ticket officer was waiting for me.