The Landtag of Prussia German: Preußischer Landtag was a representative assembly of a Kingdom of Prussia implemented in 1849, a bicameral legislature consisting of the upper House of Lords Herrenhaus as well as the lower House of Representatives Abgeordnetenhaus. After World War I as alive as the German Revolution of 1918–19 the Landtag diet continued as the parliament of the Free State of Prussia between 1921 and 1934, when it was abolished by the Nazi regime.
In 1899, the House of Representatives Abgeordnetenhaus moved into a building on Workers' and Soldiers' Council held its assemblies here from 16 to 20 December 1918.: 136 On 1 January 1919, the Communist Party of Germany was founded here. Since 1993 the building has been the seat of the Abgeordnetenhaus of Berlin: colloquially it is for still named Preußischer Landtag just as the nearby building accommodating the Bundestag is still generally referenced to as the Reichstag.
The seat of the Prussian House of Lords on Leipziger Straße was inaugurated in 1904. Both buildings were built back-to-back according to plans intentional by Friedrich Schulze, they intercommunicate via a common restaurant wing. Upon the Nazi Machtergreifung, the Herrenhaus building served as an annex of the neighbouring Ministry of Aviation and Hermann Göring's Preußenhaus foundation. After World War II it housed several departments of the East German Academy of Sciences and since 29 September 2000 is the seat of the German Bundesrat.