A German-language film loosely based on the 1883 operetta Eine Nacht in Venedig (A Night in Venice) by Johann Strauss II. The film was also made into separate Hungarian-language version Egy éj Velencében based on the same screenplay. The two versions were shot simultaneously. The Hungarian version was co-directed by Wiene and Géza von Cziffra and used a separate cast of Hungarian actors. From Wikipedia.

Eve's emotions are torn between two European princes, lifelong rivals who happen to be brothers. Eve prefers the nicer of the two princes, but this doesn't stop the other from aggressively stepping up his courtship. When the less agreeable of the two monarches takes control of the throne, he orders Eve to make an immediate choice between himself and his brother.