Bonnaroo North at Downsview Park in Toronto for 2013
No no no. Wasn't there an island of sorts that used to hold events.
I want to say the name was Christian Island.
I'm probably wrong.
Centre Island. It's a great venue for shows (Arcade Fire, Bjork) and has hosted smaller day long festivals too (V Fest for 3 years) but it would be too small to host a fest of that size and the needs of a festival that size.
Downsview is much larger (it hosted 500, 000 for SARSfest back in the day) and has recently started building a series of 2 day fests (Heavy T.O., VELD) albeit ones catering to 20-30,000 people.
This idea could definitely work for the size and needs of a festival like Bonnaroo.