Thousands of Catholics congregated from before dawn on Saturday at Portugal's Fatima shrine where Pope Francis will pray the rosary with sick youngsters, people with disabilities and inmates.
Francis arrived in the Portuguese capital Lisbon on Wednesday for World Youth Day, a huge gathering of the faithful every two to three years in a different city.
The visit ends with a papal Mass on Sunday.
The 86-year-old pontiff was to fly by helicopter for the two-hour stop in the central Portuguese town, where hundreds of thousands were expected.
Some rolled out sleeping bags the night before to get a spot as close as possible to the chapel.
Others got to the sanctuary before sunrise.
Among the crowd, Lesia Dankivna, a Ukrainian living in neighbouring Spain, wrapped herself in her war-torn country's yellow and blue flag and said she decided to travel to Portugal after she heard about the pope's visit.
"We have a lot of hope ... to see if peace comes to Ukraine," the 38-year-old said, adding she hoped Francis would pray for her country in Fatima.
The Roman Catholic Church teaches that the Virgin Mary appeared to three Portuguese children in 1917 in Fatima, which was then an impoverished farming village. It believes she gave the children three messages, the so-called secrets of Fatima.
Pope Francis made two of the shepherd children saints in 2017.
With teary eyes, 60-year-old Carlos Ribeiro, from the northern Portuguese city of Guimaraes, said he has been coming to Fatima for many years and that the huge outdoor sanctuary - one of Europe's most famous - made him feel good.
"It's a very big emotion," he said.
Francis will fly back to Lisbon afterwards for a vigil with young people on the riverside Parque Tejo, a large, shadowless outdoor area.
The Portuguese state weather agency put Lisbon on high weather alert for the weekend, with temperatures expected to reach 41 degrees Celsius (105.8 Fahrenheit) on Sunday.
