The Vienna ball, which dates back to 1814, is held at the Opera house. It takes organisers 30 hours to convert the opera house into a ballroom plus another 21 to dismantle it.
The opera ball is one of the highlights of the social calendar in Austria and is known for a guest list that includes many famous celebrities.
Since the Congress of Vienna, the city of waltzes has been famous for its legendary balls. Each year more than 450 balls take place in Vienna. The city celebrates Carnival in January and February with exuberance. The three-four rhythm is also joined by more contemporary sounds, offering enjoyable dancing for every taste.
The best time of the year begins for ball-goers and dance fans on November 11. The Vienna ball season starts punctually at the beginning of Carnival with public dancing of the waltz in the city centre. The Vienna ball season reaches its peak in January and February. The old tradition of Carnival balls continues to thrive in the city. While some dancers enjoy following the three-four time of the waltzes, others may prefer letting loose to a disco beat.
An especially large number of balls are held at the Imperial Palace in Vienna. These traditional balls adhere to a festive ceremonial pattern. The ladies appear in a long evening gown, the men wear a tuxedo or tails. Young ladies in white dresses and their gentlemen open the ball with a polonaise; the rest of the visitors are only allowed on the dance floor after the proclamation “Alles Walzer!” (Let the waltz begin!). Further show acts and interludes give structure to the night. This includes the popular “Fledermaus” quadrille by Johann Strauss. This is performed by the public to the instructions of dance teachers and ends to everyone’s amusement in a complete muddle.
Source Vienna info.