From Wikipedia: "The Magdeburg Water Bridge (German: Wasserstraßenkreuz) is a navigable aqueduct in Germany, completed in October 2003. It connects the Elbe-Havel Canal to the Mittellandkanal ("Midland Canal"), crossing over the River Elbe. The canals had previously met near Magdeburg but at opposite banks across the River Elbe. It is the longest navigable aqueduct in the world - 918 metres.
Canal engineers had first conceived of joining the two waterways as far back as 1919, and by 1938 the Rothensee boat lift and bridge anchors were in place, but construction was postponed during World War II. After the Cold War split Germany, the project was put on hold indefinitely by the East German government.
The reunification of Germany and establishment of major water transport routes made the Water Bridge a priority again. Work started in 1997, with construction taking six years and costing €500 million. The water bridge now connects Berlin’s inland harbour network with the ports along the Rhine river. The aqueduct's trough structure incorporates 24,000 tonnes of steel and 68,000 cubic meters of concrete."