Niedersächsisches Landesarchiv (Standort Oldenburg)

The Niedersächsisches Landesarchiv (until 2013: Staatsarchiv Oldenburg) of the Lower Saxony Land Archive is responsible for all state authorities and courts and their legal and functional predecessors with regional responsibility in the historic territory of Oldenburg, Germany. It takes over, preserves and maintains the documents which are handed over to state authorities, courts and other institutions of the state of Lower Saxony, and also assists archives of historically important documents from the non-governmental sector (ie municipalities, associations, companies, persons) offered to it.

More information on the German Wikipedia page

The website, in German, is.