The Douro Valley, or Rio Douro in Portuguese, is a major river in the Iberian Peninsula. Running from Spain to Porto for 850km, the valley has been established as the first wine region of the world since 1756. The landscape and the climate are prosperous for the cultivation of grapes of course; but also, almonds and olives. The Douro is mostly known for his winegrowing (vinehateiro), which has been designed UNESCO World Heritage Site.
The Douro railway station line has been completed in 1887 and runs along the river for 750 km from Porto to Pocinho. If you are leaving from Porto, check São Bento train station timetable here. The train ride takes 3h30mins from start to finish. I recommend you leave early and spend the whole day. From Porto, the return ticket costs 23.95€ (as of March 2017).
The majors cities along the track are Régua, considered a concentration point for travel by boat inside the valley or for visiting exploitation (Quintas) for wine tasting. Contact Rota do vinho do Porto for more information.
Pinhão is considered the center of Port wine. During the vintage, between September and Octobre, the town is super active. Apart from that, the city has a charming calm with restaurants.
Those pictures have been taken from the train.