Heidelberg is one of the prettiest and best-preserved towns in all of Germany, set in picture postcard perfection alongside the Neckar River, with a classic castle towering above. Filled with Old World charm, its almost like a fantasy version of an ancient German town, or something dreamed up by Disney -- but this is the real thing. Heidelbergs historic center of picturesque early 18th century buildings, about one mile long and four blocks wide, is an ideal-sized pedestrian zone to explore on foot.