The Douro is the highest-flow river of the Iberian Peninsula. It rises near Duruelo de la Sierra in Soria Province, central Spain, meanders south briefly then flows generally west through the north-west part of central Spain and into northern Portugal, to its mouth at Porto, the second largest city of Portugal. At its mouth it meets the Atlantic Ocean.
The river is notable for the scenic Douro railway line, tourism more generally and – relatedly – the creation and production of a mildly fortified wine: port, grapes, conventional wines and other agricultural produce. A small tributary of the river has the Côa Valley Paleolithic Art site which is considered important to the archaeological pre-historic patrimony, designated a UNESCO World Heritage Site.