EXCLUSIVE: Behind the Scenes With U2 on Tour!

Sept. 14, 2009— -- If you want to see a huge tour by one of the biggest rock bands of all time, look no further than U2. The pop legends just kicked off their long-awaited 360 Tour in the United States this weekend, and "Good Morning America" got exclusive backstage access.

The band's North American tour began at Chicago's Soldier Field in front of 65,000 screaming fans, on a circular stage underneath a 90-foot-tall, four-pronged canopy that lead singer Bono referred to as a "spaceship." The steel structure took four days to build and housed not only the band but a 150-foot pylon and a 54-ton cylindrical video screen that lit up the stadium.

U2 hasn't performed in open arenas in the United States in more than a decade, and the band members said they wanted to do it in a very big way. Reportedly, $40 million was spent to build the 360-degree stage. But when you put all that together with U2 in front of these American audience, the value is priceless.

"We're so exposed," said guitarist the Edge. "And when the four of us come together, there's this clear view for everybody. They can really see the interaction."

"I think, in general, the whole idea of U2 is to engage with our audience," drummer Larry Mullen Jr. said. "So we had to figure out how to do it and how to really engag. ... That's what's special about this show. It's in 360. And the audience is such a big part of what we do."

U2 played for just over two hours each night, performing 22 to 24 songs spanning the band's career. The tour is supporting their recent album "No Line on the Horizon." The Chicago Tribune called it one of the best stadium shows of the last decade.

"Chicago has just always been a great music town, hasn't it?" said bassist Adam Clayton. " You know, there was always that -- the blues musicians coming up in the '50s. And there's always something going off here. And I think it's very musician-friendly. So it's good to be back. And we've always had great audience and a great reaction."

Mullen, who started the band decades ago, says, "I didn't choose these guys. It turns out that they chose me."

He joked that he regrets not sticking with the name the Larry Mullen Jr. Band.

"In fact, that is one of my big regrets," he said. "I think we could've been bigger."

"U2 is such a crap name," added the Edge, laughing.