The Duoro River runs through Spain and Portugal and is a very important river for the Iberian peninsula. It starts in Spain near Duruelo de la sierra and ends in Portugal near Porto. The river passes through five different provinces; Tordesillas, Alamazan, Soria, Aranda de Duero and Zamora. Only a few sections of the river can actually be accessed by boat.The Douro is very important to agriculture in the area as it is used for irrigation and creates its own micro climate in the dry arid land it is in. Almonds, grapes and olives are all grown near the Douro. The grapes from this area are used in the famous wine Port and the Douro has been named its own wine region.In order to regulate the flow of the river there have been many dams build in the river in Portugal. It is in Portugal where you can travel by boat on the river and see much of the country. These dams have created a more consistent flow as well as using locks that make it very easy for boats to travel through what was once difficult river.There are many towns along the banks of the river. Some of these towns and large cities are Porto, Vila Nova de Gaia, Zamora, Valladolid, Foz Coa, Miranda do Douro and Peso da Regua. These towns have beautiful homes, castles, manor homes, churches and monasteries that can be visited.The part of the river that cannot be traveled on by boat is mainly the section that forms the boundary between Portugal and Spain. This part of the river forms narrow canyons that were historically important areas for battle. They also managed to create language barriers between two areas.The most isolated spots of the river are actually part of the Arribes de Duero Natural Park on one side and the International Douro Natural park on the other side.