Around 800,000 people visited Vienna's Donauinselfest (Danube Island Festival) on its opening day, organisers said Saturday, hoping that the sunny weather will attract even more on the second day.
"It was sensational," said a spokeswoman for the 29th annual open-air music festival, one of the biggest in Europe of its kind. Emergency services said there had been no major incidents.
Friday saw performances by British singers Marlon Roudette and James Morrison, German band Unheilig and local favourite Hubert von Goisern. Other highlights for the weekend include Scotland's Simple Minds and Germany's Silbermond.
In total, some 2,000 artists were due to provide a total of 600 hours of music on the festival's 12 stages. Entry is free and the three-day event is organised by the Austrian capital's ruling Social Democrats of Mayor Michael Haeupl.