The building entered the history books on 31 August 1990 when representatives from both German states signed the Reunification treaty here. Built in the mid 18C, this Baroque building was later modified in neo-Classical style. A doorway from Schinkel's Bauakademie has been added to the rear. Heinrich Gentz (1810-11) linked the palace to the Palace of the Princesses via a raised passageway.