#1 – Donauinselfest
Donauinselfest, held each year in Vienna, Austria, is by far the biggest music festival in the world, despite being nearly unknown in the US and UK. Held over only 3 days, Donauinselfest hosts over 2,000 acts from the hottest Austrian and international artists. In 2013, over 3 million people flooded to Danube Island to attend this enormous festival.