Artist Yoko Ono on Wednesday urged youngsters gathered at a peace event in Hiroshima to help teach the world about the experiences of the city that was devastated by a U.S. atomic bomb on Aug. 6, 1945.

The 81-year-old widow of John Lennon told roughly 300 participants: ” ‘No more Hiroshima’ is a global issue. I want you to spread the experiences of Hiroshima to the world as much as possible.”