MADRID — More than a million people poured into a central Madrid plaza on Sunday for Pope Leo XIV ’s main Mass and a procession highlighting one of the most iconic expressions of Spanish popular piety: flower carpets.

They cheered and shouted “This is the youth of the pope!” as Leo arrived for the Mass, looping around the plaza and surrounding streets in his popemobile to a crowd packed several rows deep behind barricades.

Sunday’s Mass falls 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.

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.

At a vigil service Saturday night, an estimated 600,000 young Spaniards knelt for several minutes in silent prayer alongside Leo, suggesting that there is indeed interest 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.

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 Cibeles 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.

According to Spanish organizers, the 16 flower carpets decorating the half-kilometer (mile) procession route were prepared by a Spanish florists association from Galicia. Florists used more than 30,000 flowers, most the yellow and white colors of the Holy See flag, for the carpets that feature decorations such as the Holy See keys.

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 that 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.

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AP visual journalist Helena Alves contributed.

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