The Life Ball, one of the world's biggest AIDS charity events, drew scores of celebrities from actress Charlize Theron to French fashion icon Jean-Paul Gaultier to Vienna.
The ancient Roman festival "Ver Sanctum" or "Holy Spring", was this year's theme, and the inspiration turned the neo-Gothic City Hall into a gold-drenched fantasy world teeming with paradise birds, angels and Amazonian beauties.
Among the night's shining stars was 2014 Eurovision winner Conchita Wurst, who was welcomed with loud cheers by an adoring crowd on the red carpet.
Shortly after her arrival appeared Life Ball debutante Theron with her partner, US actor Sean Penn.
"I have no idea what to expect. There is nothing comparable in the US," she said.
Other American celebrities included entertainer Paula Abdul and transgender model Carmen Carrera, who wore a heavy gown made entirely of gold chains.
Meanwhile British star Kelly Osbourne turned up in a simple black dress, admitting that she had failed to read the invitation properly and did not know "there was a gold theme".
The exuberant opening ceremony was crowned with a fashion show by Gaultier.
But amid all the glitz and glamour, there was also a stark reminder of the event's actual purpose.
Life Ball organiser Gery Keszler revealed in a tearful speech that he himself was a carrier of the HIV virus.
"I was one of the first to be infected in Austria. I want to give hope to those affected," he said at the opening of the ball.
The Life Ball, which attracts some 40,000 revellers every year, donates its proceeds to both national and international projects fighting HIV/AIDS.