For cruise travelers, the Douro stretches from the Atlantic Ocean and the port city of Porto, all the way east and south to Spain's Vega de Terron. Porto, Portugal's second-largest city, has some 2,000 years of history behind it. While it's best known for the production of port wine (wine that's fortified with the addition of brandy), it's a bustling, cosmopolitan metropolis. Being so close to the ocean gives Porto a bit of a San Francisco feel; it's every bit as hilly, street life is colorful, and occasionally a dense fog rolls in off the Atlantic.
What's most heartening about a cruise on the Douro is the small surprises. All in all, a Douro River cruise comprises so many small discoveries, small pleasures and such a generous amount of time sailing on a riverboat that you'll be lulled into a relaxing rhythm that's far away from frantic sightseeing and over-scheduled days. Chances are, you'll be dreaming of that Douro magic long after you get home.