MADRID — Pope Leo XIV honored Spain’s centuries-old tradition of religious devotion on Sunday as a “school of faith” for today, as he presided over a Mass before a million people and highlighted one of the most iconic expressions of Spanish popular piety with a procession over flower-petal carpets.

The crowd cheered and shouted “This is the youth of the pope!” as Leo arrived for the Mass at a central Madrid plaza. He looped around the plaza and surrounding streets in his popemobile to a crowd packed several rows deep of people eager to witness the first papal visit in 15 years.

Sunday’s Mass fell on the Catholic Corpus Domini feast day, which often features processions of faithful through towns and cities led by a priest carrying the Eucharist.

In Spain, as in other predominantly Catholic countries, the processions often feature elaborate floral carpets arranged along the route.

According to Spanish organizers, the 16 flower carpets decorating the half-kilometer (mile) procession route off Plaza Cibeles were prepared by a Spanish florists’ association from Galicia.

Florists used more than 30,000 flowers, mostly the yellow and white colors of the Holy See flag, for the carpets that feature decorations such as the Holy See keys.

Leo, who arrived in Spain on Saturday at the start of his weeklong visit, has been keen to highlight the long tradition of Catholic devotion here to encourage especially young generations to find their faith in a once-staunchly Catholic country where religious observance has largely been on the wane.

In his homily on Sunday, Leo honored Spain’s tradition of the Corpus Domini processions, saying the floral carpets express the “spiritual sentiments of this country” through “altars erected in the streets.”

“This is not an exhibition, a remnant of folklore or a simple display of beauty,” he said. “It is a profession of faith in the presence of the risen Lord, who is alive and continues to walk among us.”

He said the continued observance of such devotional practices points to what Spain can and should be for the world.

“Herein lies the task of Spain today and in the future: to ensure that the religiosity which has shaped and defined this country for centuries is not a museum of the past to be visited, but a school of faith from which to draw even today,” he said.

At the end of the Mass, Leo carried a gilded monstrance, or container, holding a Eucharistic host and walked over the floral carpets, as children dropped additional petals before him and the crowd tossed petals from behind the barricades.

A vigil draws huge crowds as Leo arrives

The huge turnout in Spain began the day of Leo’s arrival, when an estimated 600,000 young Spaniards attended a vigil service Saturday night.

They knelt for several minutes in silent prayer alongside Leo, suggesting that there is indeed interest in the faith among young people despite Spain’s heavily secularized society.

“Let me take the opportunity to tell all of you: Don’t ever be afraid of thinking about a vocation to the priesthood or religious life, or other services in the church!” Leo told the crowd.

Irati Valda and Javier Hormazal, a young couple, held up a cardboard sign announcing they are going to get married on June 13 and were ushered up close to receive Leo’s blessing during the vigil.

“To see so many young people together, it’s incredible. Half a million people in silence, this is something you will only live once,” Valda said.

A form of popular piety dating back centuries

For Sunday’s Mass and procession, local organizers said 1.2 million people had turned out on a brilliant spring morning at the central plaza and surrounding streets, with more trying to get in.

The tradition of laying flower carpets — and destroying them when the procession tramples them — dates back two centuries and is popular also in Latin America, where elaborate sand designs are also made. The painstaking displays are considered an offering to the Eucharist.

Poland has already had its tradition of Corpus Domini flower carpets recognized by UNESCO, and Spain’s Galicia region is trying to have its tradition listed along with other countries as part of the world’s intangible cultural heritage.

Wildly popular religious processions, pilgrimages, and feasts continue to be held in most Spanish regions. The most recognizable are Holy Week processions during the final week of Lent, where brotherhoods and robed penitents parade ornate statues of Christ and the Virgin Mary through cities, towns, and villages alongside marching bands. Such processions draw the faithful as well as droves of non-believers and tourists.

Spanish towns and cities also regularly honor local patron saints with fiestas. Religious pilgrimages to local shrines mix piety with communal festivities and music.

In Andalusia, the El Rocío pilgrimage fetches a million people who make a long, dusty journey over the Pentecost weekend on horseback and decorated covered wagons to venerate an icon of the Virgin Mary.

Leo arrived in Spain on Saturday and urged its people to put an end to polarization and work for unity. Later Sunday, he is to meet privately with members of his Augustinian religious order and address cultural leaders.