If you will have some time left you should visit Cologne and Munich too! Most of those Ctities was plain Ground after WWII but we have had some time to rebuild Those five Cities would represent all the different Lifestyles, Cultures and Architecture of Germany. To make it by Car in 20 Days could be to much: Berlin -> Hamburg ~290km (4 Hours) Hamburg -> Dresden ~500km (6 Hours) Dresden->Cologne ~570 km (8-10 Hours) Cologne->Munich ~580km (7-9 Hours).