Workers lay the dance floor in the opera house in Vienna February 10, 2015. The Viennese Opera Ball is opened by the Austrian President and features a musical programme with solists and artists from the Vienna Philharmonic and State Ballet before the 144 debutants and debutantes lead into the festivities with Johann Strauss' danube waltz. The traditional ball takes place on February 12, with tickets starting at 250 euros ($340) and a box as much as 18,500 euros ($25,000). REUTERS/Leonhard Foeger (AUSTRIA - Tags: SOCIETY ENTERTAINMENT)