Bonn
When this relaxed city on the Rhine became West Germany’s ‘temporary’ capital in 1949 it surprised many, including its own residents. When in 1991 a reunited German government decided to move to Berlin, it shocked many, especially its own residents.
A generation later, Bonn is doing just fine, thank you. It has a healthy economy and lively urban vibe.
This is from the Lonely Planet Germany.