Visiting archives in Germany: a guide to discovering and using them: Federal and State Archives

Das Bundesarchiv - The Federal Archives
The Federal Archives have the legal responsibility of permanently preserving the federal archival documents and making them available for use. This includes documents (files, papers, cartographic, records, pictures, posters, films, sound recordings and machine-readable data) arising from the central institutions of the Holy Roman Empire (1495/1806), the German Confederation (1815/1866), the German Reich (1867/71/1945), the occupation zones (1945/1949), the German Democratic Republic (1949-1990) and the Federal Republic of Germany (since 1949).
Furthermore:

• Archival records of the central leadership organs of the parties, unions and mass organisations of the German Democratic Republic (1949-1990). (=Foundation Archives of Parties and Mass Organisations of the GDR in the Federal Archives).
• Personal papers of important personages, documents of parties, associations and societies of cross regional importance, as well as published sources.

Das Politische Archiv des Auswärtigen Amtes (PA AA) - The Political Archives of the Federal Foreign Office
This archive was founded in 1920 and keeps all records concerning German foreign policy from the founding of the North German Confederation (1867) up until today.

Archiv des Bundesbeauftragten für die Unterlagen des Staatssicherheitsdienstes der ehemaligen DDR -
Archives of the Federal Commissioner for the Records of the State Security Service of the former German Democratic Republic
The archive keeps the records and documents of the State Security Service of the GDR (the "Stasi"). You may know this institution by its more common name "Gauck-Behörde" (Gauck Office) after the first federal commissioner Joachim Gauck, now President of Germany.

Geheimes Staatsarchiv Preußischer Kulturbesitz - Prussian Privy State Archives
Nowadays this archive holds about 35.000 linear metres of records mainly concerning the central institutions of Brandenburg-Prussia but also some provincial records and non-governmental documents.

Archiv der Stiftung Bundeskanzler-Adenauer-Haus - Archive of the Foundation Chancellor-Adenauer-House
This archive holds part of Konrad Adenauer's political papers ("Nachlass"), first chancellor of the Federal Republic of Germany. The archive does not have a website, but you can find all relevant information on the foundation's site.