Photos by myself. The south border of Porto is made by the river Douro. That area is called "Ribeira". It's the oldest part of the city. Porto’s historical centre it was classified by the UNESCO as “World Cultural Heritage” in December 1996, . This is a very beautiful area, with lots of tourists, restaurants and of course, Port wine cellars! The boats (Rabelo boats) were used to carry the Port wine from the Douro 's vineyards, upriver, to the city. Nowadays the wine is transported by trucks.