Panoramic view of a boat with tourists moving on the Douro River in Portugal

porto douro river boat ribeira unesco street portuguese city river cruise scenic boat ride ribeira district waterfront view historic district world heritage site cobbled streets tourism ribeiras charm riverbank beauty boat experience boat excursion picturesque streets riverside culture douro rivers banks historic neighborhood unesco recognition street scene ribeira atmosphere historical district unescolisted area quaint streets portuguese heritage traditional buildings ribeiras authenticity riverbank exploration charming streets riverfront culture exploration tour river journey view travel adventure trip excursion quaint picturesque charming historic