16 Photos You Need to See from the iHeartRadio Festival

What happened in Vegas this weekend didn't stay there! See how Taylor, Ariana, Alicia, Usher and more celebrated in Sin City

PEEK-A-BOO

Hilary Duff shows off a little skin in her cutout black dress as she presents during Saturday's show. "I'm here to have fun," Duff told radio host Elvis Duran before introducing "All About That Bass" singer Meghan Trainor. "I was going to wear a butt pad tonight, but then I didn't!" she joked.