World Youth Day (WYD) is an event for young people organized by the Catholic Church.
This holiday was initiated by Pope John Paul II in 1985, since that time WYD taking place in different countries integrating mane peoples from all over the world.
Pope Francis announced at the end of closing mass for World Youth Day 2013 in Rio de Janeiro that Kraków, Poland will be the venue for World Youth Day 2016, taking place in term 25- 31.07.16
World Youth Day is commonly celebrated in a way similar to many events. The most emphasized and well known traditional theme is the unity and presence of numerous different cultures. Flags and other national declarations are displayed among young people to show their attendance at the events and proclaim their own themes of Catholicism.
See Catholic Travel Centre very usefull introduction to Cracow
Official site of WYD
Official Twitter of WYD
Official Instagram of WYD
Official Youtube channel of WYD