If any city in Germany encapsulates the spirit of the country, it is Heidelberg, which lies 80 km (50 mi) south of Frankfurt in the southwestern state of Baden-Württemberg. Scores of poets and composers-virtually the entire 19th-century German Romantic movement have sung Heidelberg's praises. Goethe and Mark Twain both fell in love here: the German writer with a beautiful young woman, and the American author with the city itself. Sigmund Romberg set his operetta The Student Prince in the city; Carl Maria von Weber wrote his lushly Romantic opera Der Freischütz here; and composer Robert Schumann was a student at the university. The unwitting result of their efforts would warm any publicity agent's heart: Heidelberg's fame is out of all proportion to its size (population 145,000); more than 2½ million visitors crowd its streets every year. Many of those visitors pass through Heidelberg while traveling the west-east course of the Burgenstrasse (Castle Road), the 1,000 km (621 mi) path between Heidelberg's western neighbor Mannheim and Prague. The Burgenstrasse takes in nearly 70 castles and palaces along its length - Heidelberg's own majestic Schloss (castle) is a highlight. As the road approaches Heidelberg, it begins to run alongside the Neckar, a snaky river that finally flows into the Rhine near Mannheim. When most of the Schloss was built, Heidelberg was a center of political power: the Rhineland Palatinate was based here. At the end of the Thirty Years' War (1618-48), the elector Carl Ludwig married his daughter to the brother of Louis XIV in the hope of bringing peace to the Rhineland. But when the elector's son died without an heir, Louis XIV used the marriage alliance as an excuse to claim Heidelberg. In 1689 the town was sacked and laid waste; four years later it was sacked again. From its ashes arose what you see today: a baroque town built on Gothic foundations, with narrow, twisting streets and alleyways. The new Heidelberg changed under the influence of U.S. army barracks and industrial development stretching into the suburbs, but the old heart of the city remains intact, exuding the spirit of romantic Germany.