I'm considering giving an R15 a try over here in Berlin to kill a few hours and give me something fun to do... my main query is what you guys would consider to be a suitable area to cover.
You can see the network map here (PDF download)
Would you agree that the most sensible one would be just to include Zone A (inside the Ringbahn), as Zones A+B would make it stupidly big and anywhere in between would make drawing a dividing line most difficult!
Cheers
James