article: Unter den Linden
links: Mitte Berlin State Opera Kingdom of Prussia Neue Wache House of Hohenzollern Karl Friedrich Schinkel Deutsches Historisches Museum Museum Island Humboldt University of Berlin Brandenburg Gate Wilhelm I of Germany Berlin Walther von der Vogelweide World War II Hungary Linden tree Frederick II of Prussia Spree Thirty Years' War Germany Alexander von Humboldt Soviet Union