The Duero River is one of the longest rivers in the Iberian Peninsula, flowing through both Spain and Portugal. It stretches about 897 kilometers and is known for its beautiful landscapes, vineyards, and historical significance. The river starts in the Sierra de Urbión mountains in Spain and eventually empties into the Atlantic Ocean near the city of Porto in Portugal. Along its journey, the Duero River passes through several important regions, including the famous Douro Valley, renowned for its production of Port wine. The river has been a vital waterway for trade and transportation for centuries, shaping the cultures and economies of the areas it traverses.