The navigable part of the Douro river is not very long, about 130 miles, but it extends further, well into Spain. In Portugal it has five dams with locks that allow navigation from sea level up to 410 feet. The tallest of these are the Carrapetalo (118 ft.) and Valeira (105 ft.). These dams are realtively new, from the 1970s and 1980s.
© Tom Lebsack