The occasion, Europe's biggest charity event, was serious: raising money for AIDS and HIV research. But as in previous years, the 23rd Life Ball was also a free-for all gala with an emphasis on diversity.
This year's theme revolved around the ancient celebration of spring as the giver of life, and organizers pulled out all the stops. The normally sombre neo-Gothic City hall was turned into a structure glowing with light, and its square a huge stage of blazing fire, dance, song — and of music ranging from Beethoven and Stravinsky to Trevor Jackson singing "Love Child."
Tens of thousands of spectators pushed against barriers to ogle paying guests in formal dress rubbing shoulders with celebrities, party-goers dressed in little more than body paint and cross-dressers in wild costumes.
Top tickets go for 750 euros ($850) — a price that entitles holders to an all-night party inside the ornate City Hall chambers, complete with champagne and tantalizing delicacies.
For those not in tuxedoes, the colour of the evening was gold, and many of the costumes glittered correspondingly. Markus Zenner and Gerhard Grein came as fairy princes because at a party open to all "high nobility also has to be represented."
Others, like Julia, settled for little more than golden body paint. As the evening chill settled in, the 26-year old laughingly conceded that she was cold, while her near-bare partner added: "We're waiting for the party to heat up." Both declined to give full names, saying they could get in trouble with their employers.
Actress Charlize Theron was among the celebrities in attendance and took the stage to urge continued support both for her South African AIDS charity organization and the world-wide fight against HIV — a message backed by her partner, Sean Penn.
Also there were singers Paula Abdul, Mary J. Blige and Kelly Osbourne, burlesque artist Dita Von Teese — and of course Conchita Wurst, the Austrian cross-dressing winner of last year's Eurovision song contest.
Hailing the event as "one of the best nights of my life," Osbourne said: "I will do anything for this cause because it's so beautiful."
Wurst, who has become a poster person for tolerance since her song contest triumph, belted out her new torch song "You Are Unstoppable," to prolonged cheers from the crowd.
She later exchanged her simple ankle-length white skirt and skimpy top to sing "Fire Storm," another new single, in a black-and-white ball gown with a trailing cape designed by Jean Paul Gaultier for an opulent fashion show by the famed French designer.