Pope Francis jets into Panama on Wednesday for a gathering of young Catholics that will likely see him speak out strongly in defence of Central American migrants and human rights.
The festive five-day meeting with an expected 200,000 young people from around the world offers the pontiff, 82, a brief respite from a torrent of sex scandals that have jolted his papacy.
Groups of young pilgrims have been flocking into the small Central American country for days.
Wrapped in the flags of their nations, many resemble football fans on the eve of a major tournament, except this is one event in which they will be shouting for the same side.
At a Mass to open the festivities on Tuesday evening, tens of thousands of young pilgrims stood to chant "this is the youth of the Pope".
Panama's archbishop, Cardinal Jose Domingo Ulloa, told them the future of the church lay "in your vision of a better world".
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Mr Ulloa said he prayed the gathering "will be a balm for the difficult situation in which many of them live without hope, especially the indigenous youth and youth of African descent, the youth who migrates after receiving almost no response from their countries of origin".
Tens of thousands of young pilgrims attended the colourful open air mass, near the capital's historic ramparts overlooking the Pacific end of the Panama Canal.
Caravans of Central American migrants have travelled north through Mexico to the US border since October, roiling a debate over illegal immigrants and President Donald Trump's plans to build a border wall. Pope Francis previously criticised plans for the wall during a trip to Mexico.
He used the 2016 World Youth Day event in Poland to call on conservative governments in Central and Eastern Europe to soften their resistance to migrants seeking refuge from conflict in the Middle East.
"Many of the young people who are participating in the WYD are immigrants themselves," Vatican spokesman Alessandro Gisotti said. He said the Pope could be expected to speak out on the issue.
The Vatican bills World Youth Day as a chance for the Pope to reach out to young Catholics who he says "can change the world".
It is the sort of colorful event the people-friendly Argentine revels in, a world away from the strains of sex scandals that have rocked his six-year papacy, most recently in the United States, where priests and bishops in several dioceses are under investigation for decades of sex abuse of minors.
The pope met with victims of clerical sex abuse during his last visit to South America, to Chile and Peru, a year ago. The Vatican says there are no formal plans to do so on this trip.
But two abuse survivors from neighbouring Costa Rica have asked to meet with Pope Francis on the sidelines of the WYD.
Michael Rodriguez, 38, and Anthony Venegas, 33, said they sent a letter to the Pope requesting a meeting but received no reply.
"We managed to deliver a letter to the Pope with the help of another person. We told him that we would love to have an audience with him, tell him face to face what we have experienced, give him conclusive proof," said Mr Rodriguez.
The Pope will celebrate two open-air Masses in Panama City, and among the highlights of his five-day visit will be a trip to the Good Samaritan home for young HIV and Aids patients.
He will also take a short helicopter trip outside the city to Pacora to visit a youth detention centre and hear the confessions of inmates, including one serving time for murder.