<p>Port produced in the Douro Valley was once shipped downriver to the city of Porto in sailboats called barcos rabelos, anchored here along the Douro River. "We could see long cellars hunkered down on the riverbank, their slanted roofs emblazoned with the names of the port trade's biggest players: Croft, Taylor, Sandeman, Graham, Cockburn," says writer Rachel Howard. "As the light fades in the west, and the city lights come on, this is a magical time to be out strolling along the promenade that lines both sides of the river," says photographer Michael Melford.<br><br>Read more about Portugal's Douro Valley in "A Walk on the Wine Side" in the May/June 2008 issue of <em>National Geographic Traveler.</em></p>