Just look what Europe would be without the Euro. We had that before. West Germany had the Deutsche Mark (DM). It was basically the anchor currency for most European countries. Germany changed it monetary politics? Everybody tried to follow. It was like the Euro, just with different currencies and a pact to keep the exchange rates stable. Main difference: the monetary policy was made by the German Bundesbank and not the ECB. Though both are in Frankfurt/Germany, the ECB is an European institution.