"You don't know you're beautiful!" This image appears in the gallery:One Direction, Ariana, Avicii & More! The MUST-SEE Pictures From Capital's Summertime Ball 2015 17. "You don't know you're beautiful!" Picture: Danny North 171 images See the full gallery: One Direction, Ariana, Avicii & More! The MUST-SEE Pictures From Capital's Summertime Ball 2015