Begins in the Swiss Alps, passes through Lake Constance (in German, the Bodensee), flows west along the German-Swiss border, then turns north to form part of the German-French border. The river then flows north and joins with the Meuse and Scheldt to enter the North Sea at a delta in the Netherlands. Cities along its course include Basel, Strasbourg, Mainz, Bonn, Cologne, and Rotterdam, and tributaries include the Main, Mosel, and Ruhr. The Rhine has played a strategic role in most German conflicts since the time of the Gallic Wars but was not established as an international waterway until the Rhine Commission of 1815. German myth tells of the Lorelei, a nymph who lured sailors on the Rhine to their deaths.