an Entity references as follows:
Agnes von Hohenstaufen is a German-language opera in three acts by the Italian composer Gaspare Spontini. The German libretto is by Ernst Benjamin Salomo Raupach. It was first staged at the Königliches Opernhaus, Berlin, on 12 June 1829. Raupach categorised Agnes von Hohenstaufen as a historical-romantic opera and it is one of a number of German works of the time set in the Middle Ages (others include Weber's Euryanthe, Wagner's Tannhäuser and Lohengrin and Schumann's Genoveva). Agnes also contains many of the features that would be characteristic of French Grand Opera. Spontini substantially reworked the piece for a revival in 1837.