Claim: Söse Dam in Lower Saxony (the second-largest state by land area), Germany was opened in 1928.
Evidence: The Söse Dam is a dam in the Lower Saxon part of the Harz mountains near Osterode in the German state of Lower Saxony. It was the first modern dam and reservoir complex (German: Talsperre) to be built in the Harz and was constructed by the Harzwasserwerke between 1928 and 1931. Germany Lower Saxony 1928
(Harzwasserwerke) 1931