Rapper Lupe Fiasco joined a team of musicians, actors, U.N. ambassadors and scientists, climbing to the peak of Mount Kilimanjaro this past January in order to raise awareness about the world's clean-water crisis.

The Chicago MC said that, while the trip was one of the most difficult trials of his life, the biggest difficulty he faced was mental. "It probably is the most difficult thing I've ever done. It wasn't the altitude sickness; it was more so the battle of myself," he explained. "Battling, getting the variables right, working the math out about how much water you're going to drink, how hard you're going to push yourself, how mad you're going to get, how much you're going to think about going home."

Lupe climbed the mountain with fellow artists Santigold and Kenna, the latter who organized the entire effort, alongside actors Jessica Biel and Emile Hirsch.

The rapper also noted that his prior training in martial arts helped him to conquer the peak."I guess it was one of them 'Karate Kid' moments, you know? I did martial arts for, like, 20 years. My father was a Grand Master for, like, 40 years before he passed. It's just one of those lessons that we were taught," Lupe said. "We used to run in the snow barefoot, jump over cars, hang out of trees and do all types of crazy stuff, and that was just part of the training, to understand that it's you versus yourself. The terrain is always going to exist, it's always going to be there, and it's whether you are capable enough to go through it ... Just some little mysticism right there, a little bit of that karate magic to keep the mind going."

"There's strength in numbers," Lupe said, of his decision to join the group. "It's about mass. You can have one person, and he looks cool holding up a sign, but it's much better when you have 500 people holding up the same sign," he said. "There was actually, like, 300 people involved in this climb, and that's what it took to get everyone to the top. And that's what it's going to take to change this global water situation."

An MTV special about the climb, 'Summit on the Summit: Kilimanjaro,' aired on March 5. Watch the trailer here.