The Amur is the longest border river in human history: Over a stretch of two thousand kilometres, it separates two superpowers, Russia and China. In China, the meandering Amur is called the Black Dragon. Ferries cross between the only two cities along the Amur's middle course, Blagoveshensk and Heihe, but not a single bridge links the countries. The border land along the Amur and some of its tributaries offer sanctuary to wildlife, and it's also the border situation that has, so far, kept the Amur free of hydro-electric dams.