Today you may take an optional full day excursion to two small Bohemian Czech cities: Budweis, with its impressive town square featuring Gothic, Renaissance and baroque buildings, and Cesky Krumlov, a UNESCO World Heritage Site. Founded by a Bohemian king in the 13th century, Budweis was for a time the royal brewery for the Holy Roman Emperor, and beer remains a major industry there. Founded at about the same time as Budweis, Cesky Krumlov is known for its unusually large castle, and is an important cultural centre, hosting various festivals throughout the year. Or, join a morning walking tour of Passau's Italianate Old Town area, passing by the Veste Oberhaus, a 13th-century fortress that served as a bishops' stronghold for several centuries. Enjoy a concert on Europe's largest pipeorgan in St. Stephan's Cathedral, then relax on board before dinner.