The Douro or Duero (Latin: Durius, Spanish: Duero, Portuguese: Douro, pron. 'doɾu) is one of the major rivers of the Iberian Peninsula, flowing from its source near Duruelo de la Sierra in the province of Soria across northern-central Spain and Portugal to its outlet at Porto. Its total length is 897 km, of which only sections on the Portuguese river are navigable by light rivercraft.
In its Spanish section, the Duero crosses the great Castilian meseta and meanders through five significant provinces of the autonomous community of Castile-Leon: Soria, Burgos, Valladolid, Zamora, and Salamanca, passing through the towns of Soria, Almazán, Aranda de Duero, Tordesillas, and Zamora.
This region, for the most part, is one of semi-arid plains planted with wheat and in some places, especially near Aranda de Duero, in wine grapes, in the Ribera del Duero wine region. Sheep rearing is also still important.
Then, for 112 km, the river forms part of the national border line between Spain and Portugal, in a region of narrow canyons, making it an historical barrier for invasions and a linguistic dividing line. This isolated area has now a protected status: the International Douro Natural Park.
Once the Douro enters Portugal, major population centres are less frequent. Except for Porto and Vila Nova de Gaia, at the river mouth, the only population centres of any note are Foz do Tua, Pinhão and Peso da Régua. Tributaries are small and flow into canyons to enter the larger river. The most important are the Côa, the Tua,the Sabor ,the Corgo ,the Tavora,Paiva,the Tâmega and the Sousa. None of these small, fast flowing rivers are navigable. The Douro vinhateiro,an area of the Douro Valley in Portugal was classified by UNESCO as a World Heritage Patrimony Sight.
These reaches of the Douro have a microclimate allowing for cultivation of olives, almonds, and especially grapes important for making the famous Port wine. The region around Pinhão and São João da Pesqueira is considered to be the centre of Port wine, with its picturesque quintas or farms clinging on to almost vertical slopes dropping down to the river. Many of these quintas are owned by multinational wine companies and are worth a visit.
Traditionally, the wine was taken down river in flat-bottom boats called rabelos, to be stored in barrels in cellars in Vila Nova de Gaia, just across the river from Porto. In the 1950s and 1960s dams were built along the river ending this river traffic. There are nine dams on the Portuguese Douro alone making the flow of water uniform and generating hydroelectric power. Now Port wine is transported in tanker trucks.
In Portugal, the Douro flows through the districts of Bragança, Guarda, Viseu, Vila Real, Aveiro and Porto. Porto is the main hub city in northern Portugal and it`s historic centre is declared as a UNESCO monumental place.
The railway Linha do Douro connects Porto, Rio Tinto, Ermesinde, Valongo, Paredes, Penafiel, Livração, Marco de Canaveses, Régua, Tua and Pocinho. Pocinho is near the city of Foz Côa, wich is close to Vale Arqueológico do Côa, (an Archaeological pre-historic patrimony)another UNESCO Heritage Sight.
Major riverside towns: Soria, Almazán, Aranda de Duero, Tordesillas, Zamora (Spain); Miranda do Douro, Foz Côa, Peso da Régua (most frequently known as Régua, Lamego, Vila Nova de Gaia, (usually simply known as Gaia) and Porto (Oporto) (Portugal).
The most populous cities along the Douro are Valladolid, Zamora (in Spain) and Porto and Gaia, (in Portugal). The latter two are located at the mouth of the Douro, which is the second largest river in the Iberian Peninsula (The Tagus or Tejo river is the largest in the Iberian Peninsula).