Electric Daisy Carnival 2012
At first, it was a one day event, then in 2009. it was expanded into two days bringing 130.000 people!!! The Las Vegas event lasted 3 days in 2011. and had around 65-80.000 people per day!
The first Electric Daisy Carnival was held in 1997 at the Shrine Expo Hall. In 2009. the festival is brought to Puerto Rico. In 2010 the event expanded to include Dallas, Texas, and in 2011, an event in Orlando, Florida was added.
The festival itself usually has multiple stages, full of a variety of electronic dance music, talented performance artists and visual delights.
As always, you can find more relevant info here.