Taxes being one of them.  Upon visiting the Rheingau, one will notice all the magnificent castles on the hillsides along the river.  These were owned by the most influential Dukes from the 12th to 15th centuries.  For centuries, the Rheingau River was the major route for transporting wines from the city of Mainz in the Rheingau downriver to Cologne, which was an important trading center for wines.  The Dukes participated in this commerce by exacting tolls for all ships that passed along this route, which effectively doubled the cost of wines, including those of …