Prif afon y wlad yw Afon Donwy, ac ers iddi gael ei chysylltu gan gamlas ag afon Main ym 1992, gellir eludo nwyddau o'r Môr Du i Fôr y Gogledd.
The great river of Hungary is the Danube which, following its linking to the River Main by canal in 1992, enables goods to be carried from the Black Sea to the North Sea.