The Donauinselfest (German for Danube Island Festival) is a free open-air music festival taking place annually at Donauinsel in Vienna, Austria and it's hosted by SPÖ Wien. 

Donauinselfest was started in 1983 by the Social Democratic Party of Austria. In the first year 160,000 people attended and the festival lasted one day. With over 3 million visitors in 3 days, it's the biggest open-air music festival in the world.

Performances take place on the festival area at a length of 4.5 km on 11 different open-air stages and in 16 tented areas around the island. Local bands and DJs as well as many world-famous artists have performed since 1984.

Around 1500 volunteer assistants and visible police presence help make the Donauinselfest one of the most secure events in Europe.

There are areas (called "islands" as well) which are usually sponsored by radio stations, newspapers and other companies. These are spread out over a 4.5 kilometer area. Musicians of an extremely broad range of genres perform.

The layout is roughly the same every year, with some stages being removed or added. The musicians also tend to come back every year, or being replaced by other ones that are popular.

To ensure safety of visitors, "house rules" were introduced in 2007 and checkpoint controls established to help control certain items (such as glass and liquor inside the festival perimeter). 

Food kiosks serve various national and alternative dishes including Thai, Greek, Italian, Indian, Turkish, Vegetarian and Austrian cuisine. Although all concerts are free, financial experts calculate Vienna's economy benefits from this event by almost €40 million, due to the increased tourism. 


According to en.wikipedia