(CNN)Here's some background information about World Youth Day, a day when Catholic youth and young adults between ages 16-35 gather to celebrate their faith.
World Youth Day was created by Pope John Paul II after large turnouts at the 1984 Jubilee of Young People and the 1985 gathering for the International Year of Youth in Rome.
1986 - Rome, Italy
Over 500,000 attendees
Over 1 million attended mass at Longchamps Race Track.
Pope at mass: "there is more to life than films and pop music."
Up to 5 million attended mass.
Pope had to use a helicopter to get to the stage.
Over 2 million attendees
Dubbed the "Catholic Woodstock"
Featured concerts and prayer services.
300 portable confessionals were set up around the Colosseum and Circus Maximus arena.
2000 priests were on hand to hear confessions in over 30 languages.
800,000 attended mass presided by the Pope.
Sydney, Australia. Pope Benedict XVI makes his first trip to Australia to deliver the final Mass at the gathering.
Spain is the first country besides Italy to host WYD for a second time.
Rio de Janeiro, Brazil
3 million attend the final Mass.
2.5 to 3 million attend the final Mass.