Hauptstaatsarchiv Weimar

Founded in 1923, the Thuringian Central State Archive Weimar is based in two buildings in Weimar.

It contains the archives for Thuringia and its predecessors, including the Duchy of Saxe=Weimar and the Ernestine territories, and is the largest of the six Thuringian state archives.

More information on the German Wikipedia page.

The website, in German, is