This complex was designed by Knobelsdorff to garner unprecedented artistic and scientific influence for the Prussian monarchy. The site was to include an opera house, an academy of science and a castle. Only the opera house was built, as Friedrich II favoured Potsdam. Since then, several changes have transformed the square, the latest of which (in 1994) was the construction of the Versunkene Bibliothek (“Sunken library”), which commemorates the Bebelplatz auto-da-fé of 10 May 1933.