Berlin has a network of cycling routes. There's a few long distance routes passing through or starting in Berlin, as well as some local routes. Routes should probably be mapped as relations following Relations/Routes.
- (de) Deutschsprachiges OSM-Portal für Radfahrer
Long distance routes
- R1 is mostly complete.
- Berlin-Leipzig (Status) 
- Havelradweg [Havelradweg ab Mauerradweg bis Havelberg als relation HVL getagt--Makracht 06:31, 5 August 2008 (UTC))
Radial routes (ref=RRx), tangential routes (ref=TRx), Mauerradweg (currently mapped as ref=Mau). Radial routes start at Schloßplatz.
- RR1 and Mau are partially there.
- RR2 (Gatow), RR3 (Spandau), RR8 (Hellersdorf) exist, but are missing
- planned routes (in construction?) RR 12 (Teltow), TR 4 (Dahlem-Biesdorf), RR7 (Ahrensfelde), RR6 (Bernau) (part of Berlin-Usedom?), TR 2 (Jungfernheide-Hohenschönhausen)
It's hard to actually see these routes as routes on the ground: RR1 from Mitte to Wannsee isn't marked as RR1, there's just signs towards Wannsee in one direction and towards Mitte in the other. You can't really see which route you're on. So perhaps it's not such a good idea to actually tag the routes in this way?
As an example, RR1 and RR12 share the same route from Schloßplatz to Innsbrucker Platz. There's no indiciation that these are actually two separate routes.