Completed in 1993 after a thousand years of planning, the Main-Danube Canal finally links, well, the Main and Danube Rivers. Its is about 170km in length, was hideously expensive, but now allows river transport from Amsterdam to the Black Sea. The European watershed is marked by a large concrete wall (no, not across the canal) at about half way. Rain falling on one side flows to the Black Sea, and on the other to the North Sea. There are ducks and very, very big locks.