Portugal's Duoro, still a very new river destination, offers an alternative to Europe's well-known Rhine-Rhone-Danube standards. Cruises here begin and end in the UNESCO heritage city of Porto, which, of course, is known for producing Portugal's famed port wine (and its numerous port wine houses for tastings). But there's more to vineyards and tastings on the Duoro. There's history in the UNESCO city of Porto, ambience in Spain's Salamanca, built from golden sandstone (Columbus studied at its 13th-century university), and charming Castelo Rodrigo, a 12th-century walled village in the mountains that's surrounded by olive groves and wild lavender. Uniworld is the major operator here, with cruises from spring through fall on its brand-new 128-passenger Duoro Spirit.
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