Ticket to ride
I never knew that bicycles needed a ticket on the train/metro/whatever you call it in Berlin and found it quite funny. Yes, my bike and I took the train to the forest and we both got lost in there. It was amazing.
If you ever visit Berlin, I would encourage you to make time (a day at least), rent a bike and go around Grunewald. It is massive and super green (getting green during spring). We rode from the station across the forest to the river. It was so beautiful almost made me tear up cycling down the path. We also came across a big green spot where people were laying naked under the sun. That was definitely a scene.