U2 Vertigo Tour - Croke Park, Dublin, Ireland - June 2005. During the intro to "One," the lights would go down and Bono would ask everyone to hold up their cell phones and then use them to sign a petition to end extreme poverty in the 3rd world. (For more info: http://www.one.org.) The whole stadium lit up like the night sky. It was gorgeous and surreal to finally see a U2 show in Dublin.