When we arrived in athens and caught the train into town from the airport either we did not think about it, did not see or just forgot to validate our 5 euro ticket.
We were on the train and along came the ticket validators - they wanted to see our ticket so we showed them and they said that they have not been validated and that is a fine!
A man on the seat opposite also did not validate his ticket.
For some reason instead of fining up they said we had to get off the train and validate the ticket and catch the next train.
So we were very very lucky as the fine is 60 times the fare price.
60 x 5 euro = 300 euro each