The Rio Douro is a major river in northern Portugal and Spain, flowing approximately 897 kilometers. It originates in the Sierra de Urbión mountains in Spain and travels westward, eventually emptying into the Atlantic Ocean at Porto. The river is known for its stunning landscapes, steep terraced vineyards, and historical significance in the production of Port wine. The Douro Valley, through which the river flows, is a UNESCO World Heritage site, recognized for its cultural and agricultural importance. The river is also a popular destination for river cruises, offering scenic views of the surrounding hills and charming villages.