Original: The Greater Berlin Act ( ) , in full the Law Regarding the Reconstruction of the New Local Authority of Berlin ( ) , was a law passed by the Prussian government in 1920 that greatly expanded the size of the German capital of Berlin .
Simplified: Its area went from to and the population doubled from approximately 1.9 million to near 4 million , with almost 1.2 million of these new inhabitants coming from the 7 surrounding towns alone .