Eurail System

What is the most beautiful area of Germany?
I am talking about castles and such that are easily accessible (just outside a big city or accesible by Eurail train system). Thank you!
I love the area around munich. from here you can get to the castles (lindhof/newschanstien are both an excellent day trip by train+ bus), the romantic road and rothenburg, and salzburg (great castle/fortress above the city + mozart + cathedrals & pedestrian areas) all quite easily. The metro will take you to the town of Dachau and you can take a bus to the concentration camp there for a solem reminder of the dark side of man
… I came back to see what others thought and agree that Berlin and Dresden are “must see” cities Koln is also a fav but geographacilly seperate.