The Douro River, the heart of Porto.
The Douro River (Portuguese: Douro) or Duero River (Spanish: Duero) is one of the most important rivers on the Iberian Peninsula. It serves as a border between Spain and Portugal, with a total length of 897 km, of which 112 km make up the border between the two countries. In Portugal, small boat tourism is possible. The river flows from Spain through Portugal and out into the Atlantic Ocean at Porto, hence the names vary between the two countries.
Tourist destinations themed around the Douro River are gaining popularity. The upper valley of the river is already known to locals as a great spot for outings. Porto, Portugal's second-largest city, is the most notable nearby city, and the old city of Porto along the Douro River, as well as the wine-producing region of the upper Douro Valley, have been designated as UNESCO World Heritage Sites.