|Douro (Portuguese), Duero (Spanish)|
|Source||Picos de Urbión|
|- location||Sistema Ibérico, Duruelo de la Sierra, Soria, Castile and León, Spain|
|- elevation||2,157 m (7,077 ft)|
|Mouth||Foz do Douro|
|- location||Atlantic Ocean, Porto, Greater Porto, Norte, Portugal|
|- elevation||0 m (0 ft)|
|Length||897 km (557 mi)|
|- average||714 m3/s (25,215 cu ft/s)|
|- max||17,000 m3/s (600,349 cu ft/s)|
|Discharge elsewhere (average)|
|- Pocinho||442 m3/s (15,609 cu ft/s)|
|Wikimedia Commons: Douro River|
The Douro (Portuguese: Douro [ˈdowɾu, ˈdoɾu]; Spanish: Duero [ˈdweɾo]; Latin: Durius) is one of the major rivers of the Iberian Peninsula, flowing from its source near Duruelo de la Sierra in Soria Province across northern-central Spain and Portugal to its outlet at Porto.
The name, Latinized Durius, may have come from the Celtic tribes that inhabited the area before Roman times: the Celtic root is *dubro- and in modern Welsh dŵr is "water" with cognate dobhar in Irish.
The Douro vinhateiro, an area of the Douro Valley in Portugal, has been classified by UNESCO as a World Heritage Site. 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 on Spanish and border sections. Now Port wine is transported in tanker trucks.
It is the third longest river in the Iberian Peninsula after the Tagus and Ebro; its total length is 897 kilometres (557 mi), of which only sections of the Portuguese extension are navigable, by light rivercraft.
In its Spanish section, the Douro crosses the great Castilian meseta and meanders through five provinces of the autonomous community of Castile and León: Soria, Burgos, Valladolid, Zamora, and Salamanca, passing through the towns of Soria, Almazán, Aranda de Duero, Tordesillas, and Zamora.
In this region, there are few tributaries of the Douro. The most important are the Pisuerga, passing through Valladolid, and the Esla, which passes through Zamora. This region is generally semi-arid plains, with wheat and in some places, especially near Aranda de Duero, with vineyards, in the Ribera del Duero wine region. Sheep rearing is also still important.
Then, for 112 kilometres (70 mi), the river forms part of the national border line between Spain and Portugal, in a region of narrow canyons, making it a historical barrier for invasions and a cultural/linguistic divide. In these isolated areas, in which the Aldeadávila Dam impounds the river, there are protected areas: the International Douro Natural Park (on the Portuguese side) and the Arribes del Duero Natural Park (on the Zamoran margin).
The Douro fully enters Portuguese territory just after the confluence with the Águeda River; 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 here are small, merging into the Douro along the canyons; the most important are Côa, Tua, Sabor, Corgo, Tavora, Paiva, Tâmega, and Sousa. None of these small, fast flowing rivers are navigable.
Human geography 
Major Spanish riverside towns include Soria, Almazán, Aranda de Duero, Tordesillas, Zamora and major Portuguese towns include Miranda do Douro, Foz Côa, Peso da Régua, Lamego, Vila Nova de Gaia, and Porto. The most populous cities along the Douro River are Valladolid, Zamora in Spain and Porto and Vila Nova de Gaia in Portugal. The latter two are located at the mouth of the Douro.
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 its historic centre is declared as a UNESCO monumental place.
These reaches of the Douro have a microclimate[specify] allowing for cultivation of olives, almonds, and especially grapes that are 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 quintas (or farms/estates) that extend the almost vertical slopes along the river valleys. Many of these quintas are owned by multinational wine companies.
Recently, a prosperous tourist industry has developed based on river excursions from Porto to points along the Upper Douro valley.
There are five dams on the Portuguese Douro alone functioning to make the flow of water uniform, generate hydroelectric power, and allow navigation. Ships with a maximum length of 83 metres (272 ft) and width of 11.4 metres (37 ft) can pass through five locks. The highest one on Carrapatelo dam has a maximum lift of 35 metres (115 ft). Level of Pocinho lake reaches 125 m a.s.l.
The Douro railway line (in Portuguese: Linha do Douro) was completed in 1887; it connects Porto, Rio Tinto, Ermesinde, Valongo, Paredes, Penafiel, Livração, Marco de Canaveses, Régua, Tua and Pocinho. Pocinho is near the city of Foz Côa, which is close to Côa Valley Paleolithic Art site, (an Archaeological pre-historic patrimony) another UNESCO Heritage Sight.
The Upper Douro valley where Port wine grapes grow
The typical rabelo boat and Porto historical district in background
Port wine signs by the Douro River
Panoramic view of Oporto
The river mouth from Porto's Crystal Palace Gardens, facing west