Set among lovely tree-covered hills along the Neckar River, Heidelberg is one of Germany's most romantic cities. But be warned: It draws fleets of tour buses in the summer. Crowning the city is Heidelberg Castle, a menage of Gothic, Renaissance and baroque styles. It has towers, turrets, a courtyard and gardens. Notice how the stone changes colors depending on the angle of the sun. A big draw is the Grosse Fass (1751), a massive wine keg and a tribute to the local princes' favorite drink. To get up to the castle, take the cable car near Kornmarkt.
After visiting the castle, stroll along Hauptstrasse and see the rest of the old section of town. (If you have a car, park it at a garage outside the inner city or you'll go crazy trying to find your way through the maze of small, one-way streets.) You can get a good view of the city and the castle by crossing the bridge and walking the Philosophenweg, or Philosopher's Way (a scenic, winding path). If you have time, visit the Kurpfalzisches Museum to see an ethnology exhibit with the 600,000-year-old jawbone of Heidelberg Man, and works by Weyden and Durer. Heidelberg can be seen as a day trip from Frankfurt.
55 mi/85 km south of Frankfurt.