Crowds at the Vatican celebrated the unprecedented double canonization of Popes John XXIII and John Paul II.

Pope Francis waved to the masses who rejoiced as he enrolled John XXIII and John Paul II "among the saints."

For those in St. Peter's Square, it was a once-in-a-lifetime event.

The ceremony overflowed into the streets as far back as the Tiber River.

The historic double-canonization involved four popes in one ceremony.

Pope Emeritus Benedict XVI, who has lived in near-isolation since his retirement, also celebrated the new sainthood of his predecessors.