Who rules Germany?
President of Germany
Germany has a parliamentary system of government in which the chancellor is the nation's leading political figure and "de facto" chief executive. The president has a mainly ceremonial role, but he can give direction to general political and societal debates and has some important "reserve powers" in case of political instability (such as those provided for by Article 81 of the Basic Law). The German presidents have wide discretion about how they exercise their official duties.
Politics of Berlin
Berlin is the capital of the Federal Republic of Germany. The President of Germany, whose functions are mainly ceremonial under the German constitution, has his official residence in Schloss Bellevue. Berlin is the seat of the German executive, housed in the Chancellery, the "Bundeskanzleramt".