Scavenger hunt

After purchasing a train ticket, we had to find a machine that punches the ticket before you get on the train. The last conductor took pity on us and didn't fine us the price of the ticket (170 euro) + 30 euros for not following this unspoken rule. Asked two people about this machine, one person speculated to it's location, and we found it eventually. It worked for us, but not for the lady after us.