Sitting in the Neckar Valley, Heidelberg, is home to the oldest university in Germany. Ruprecht-Karls-Universität (est. 1386) is one of the most prominent universities in the world, ranking right up there with schools like Harvard, Cambridge, and McGill.
From Frankfurt HBF, Scott and I took a slow, direct train to Heidelberg. On they way back we had to change trains at Bizmarckplatz. In the town itself, transportation is pretty simple. The #33 bus goes from the train station to old town. In terms of sights, the main destination is Heidelberg Castle. Also near the town are remnants of an ancient wall that Celts built to keep Germanic tribes out.
Heidelberg is a great German city to visit. If you ever have to eat food, this is a solid place to replenish. From Bavarian restaurants and pubs to local student cafes, this town has it all when it comes to cuisine.