FATIMA -- As the weekend of July 29-30 approached, various groups of young pilgrims from the Archdiocese of Boston made their way to Portugal for the beginning of World Youth Day.

World Youth Day is a worldwide encounter with the pope held every few years in a different country, drawing hundreds of thousands of young people from around the world. This year, it is being held from July 28 to Aug. 7 in Lisbon, the capital of Portugal.

Of those pilgrims from the Archdiocese of Boston, about 170 are traveling with an archdiocesan group, while another 200 come from Neocatechumenal Way communities, and dozens more planned trips through their parishes or other organizations.

Mary Ellen O'Shea of Amesbury is leading a group of 12 pilgrims from All Saints Parish in Haverhill, where she serves as an extraordinary minister of Holy Communion. Her pastor, Father Christopher Wallace, asked her to be a chaperone on the trip, and when she agreed, she found herself becoming a key fundraiser and team leader.

Their group has six young people, five of whom had never traveled internationally until now. O'Shea said she thinks the trip is an adventure for them, "both spiritually and culturally."

"They are being exposed, for the first time in their life, to one, holy, catholic, apostolic, global faith," O'Shea said in a July 31 phone interview.

She said witnessing that is "the greatest thanks" she could receive.

"Watching them not just grow in the faith but grow in faith with the world is my gift from them," she said.

One of the adult pilgrims in the Haverhill group is Andrea Fogarty, a 49-year-old police captain who has been battling cancer for three years. Her focus over the last several months, through hospital stays and surgeries, has been attending World Youth Day. O'Shea has promised to take Fogarty to Lourdes after they complete this pilgrimage.

"We're all praying for a miracle from Our Lady of Fatima for Andrea," O'Shea said.

Upon arriving in Portugal, the first item on the Boston pilgrims' itinerary was a visit to Santarem, the site of a Eucharistic miracle in the 13th century. They were able to visit the church and museum where the miracle took place -- and where the relic, a consecrated host that flowed with blood, is kept to this day.

"We all got a chance to literally be in the presence of this miracle, which was really profound," Ann Gennaro said in a phone interview. Ann is a content and communications specialist and is documenting the trip for the archdiocese's social media.

O'Shea said she thought the visit to Santarem and the "amazing visual of being that close to a miracle" helped "set the tone" for their hearts and minds.

"All of us came out of there saying, 'We are now true pilgrims and true Catholics.' And to start your pilgrimage witnessing where a miracle took place, there is no greater beginning than that," she said.

They journeyed on to Fatima, the famous site of the 1917 Marian apparitions to three young shepherd children. Much of its infrastructure was built to accommodate the many pilgrims who came there after the miracles that took place.

The pilgrims spent a few nights in Fatima, staying at hotels near the square, close to the shrine to Our Lady of Fatima. Candlelight processions are held there every Saturday and Sunday night, giving the pilgrims opportunities to pray with other people from around the world.

In the morning of July 30, the pilgrims attended an international Mass at the shrine celebrated by Cardinal Seán P. O'Malley, with many other clergy from the Archdiocese of Boston concelebrating.

O'Shea went to the shrine early in the hope of securing a front-row spot for Fogarty's wheelchair. A group of pilgrims from Orlando moved back to allow her group the first few rows. O'Shea said one of the young women in her group was struck by the fact that there were thousands of people in the rows behind them, yet they were at the front, with the familiar faces of Cardinal O'Malley and Father Wallace before them.

The cardinal delivered most of his homily in Portuguese, but he spoke briefly in English. He acknowledged that that day, July 30, was his 20th anniversary of becoming the archbishop of Boston.

"It was really cool to celebrate that with him in a very unique way, in a special way," Gennaro said.

The pilgrims then received tours of Fatima, including the village of Aljustrel and the houses where the children to whom the Blessed Virgin appeared -- where Ven. Lucia dos Santos and Sts. Francisco and Jacinta Marto lived. Stations of the Cross now mark the way to the site of the Marian apparitions.

"It was a very beautiful experience," Gennaro said.

She observed that the candlelight vigil that night was more crowded than the previous night, as more pilgrims were arriving for World Youth Day, showing "the growing presence of the universal Church." Some waved their countries' flags in the procession around the courtyard.

On July 31, the Boston pilgrims headed to Lisbon, where they would have a few days to explore the city before the arrival of Pope Francis and related cultural and catechetical events.

O'Shea's group brought bracelets and other items to exchange as gifts with those they met on their pilgrimage. Some of the bracelets had the parish's name, and some had the name of the archdiocese in the colors of the Portuguese flag. She said they were already running out of gifts after just a few days of travel.

"Those are going fast. It's a beautiful exchange of faith and friendship," O'Shea said.

She said she is looking forward to seeing Pope Francis, who was to arrive Aug. 3. She has seen him before, on a visit to her native Sicily, but it will be the first time the young people in her group see him in person.

"I think that is going to be the highlight of their pilgrimage," O'Shea said.