The Mosel River in German like may rivers as a series of lochs to regulate ship traffic. our girls were very interested in how they worked so we stopped to check them out. The lochs all have two channels on one side as well as a hyrdo-power plants on the other. While checking this out, the gentleman from the control tower came down and invited us all up to watch a ship come throughout eh channel. He explained how everything worked and even let my daughter work the controls to close the gates and fill the loch/ It was a remarkable experience i am sure they will not soon forget!