This iconic waterway stretches for 550 miles from Porto on Portugal’s west coast to Spain’s Sierra de Urbión mountains, with the stunning Douro Valley wine region as the star of the show. Step ashore to enjoy a port wine tasting in Porto; ride the Historic Douro Train from Pinhao’s azulejo-tiled station; visit Peso de Regua’s grand Mateus Palace and sip coffee at Café Novelty in Salamanca’s Plaza Major.