The cities you listed are 3 times older than even the idea of an American continent. They are culturally rich and unique in their own way. They have survived se

The cities you listed are 3 times older than even the idea of an American continent. They are culturally rich and unique in their own way. They have survived several countries around them and are historically significant regardless of their size today. Cologne for example is the 4th biggest city in Germany and 2000 years old. They have traditions the rest of Germany finds odd and a strange beverage they seem to think of as beer. If that isn't enough for you culturally, than Germany really cannot compete. I don't see any reason to create some artificially big city for the sake of competing world-wide. Also you forgot that those cities are often very close to each other. The Rhein-Neckar (Mannheim, Heidelberg, Ludwigshafen), Rhein-Main (Frankfurt, Darmstadt, Wiesbaden, Mainz etc.) or Ruhr (too many to count really) area do form hubs, which can compete worldwide and are economically MUCH stronger than Berlin ever will be.