The castle in Act 2 could look like this. Spiral staircase leading to the "stage" where princess, prince, and Rusalka have their quarrel. Rusalka runs down the steps to the fishpond. Castle is located up high near the moon to imply that being with the prince is a far-fetched dream.
The Crown of Empress Eugénie was the consort crown of Eugénie de Montijo, the empress consort of Emperor Napoleon III of France. Though neither she nor her husband underwent a coronation a consort crown was specially created for her. After her husband was overthrown in 1870, following the Franco-Prussian War, Napoleon and Eugénie lived in exile in the United Kingdom. She died in 1920. She was the last surviving French person to have worn a crown. Though most of the French Crown