Pope Leo XIV celebrated Mass in the Basilica of La Sagrada Familia in the city of Barcelona, and inaugurated the sixth and last of the big towers of the basilica—the Tower of Jesus Christ—on the evening of June 10, the 100th anniversary of the death of Antoni Gaudí, the architect who designed it.

This high moment of the pope’s visit took place in Barcelona, at the end of his fifth day in Spain, in the presence of King Felipe VI and Queen Letizia, the monarchs of this majority Catholic country. 

The importance of this moment was also highlighted by the presence of Spain’s prime minister, Pedro Sánchez. La Vanguardia, the main daily newspaper here, noted that it was the first time that Sanchez has been at a ceremony in a church since he became head of the government eight years ago. Twenty government ministers were also present as were the presidents of the government and parliament of Catalonia, as well as other dignitaries including the mayor of Barcelona and the head architect of the basilica, Jori Faulí.

The cardinal archbishop of Barcelona, Juan José Omella, concelebrated the Mass with the pope, together with several other cardinals and some 250 bishops. They were joined by 4,000 worshippers inside the basilica and another 4,000 outside.

Leo is only the second pope to celebrate Mass here, the first being Benedict XVI who consecrated the church and designated it a minor basilica on Nov. 7, 2010. Today, Leo not only presided at the Mass but, after it ended, he also inaugurated the Tower of Jesus Christ, the last of the six central towers to be added to this magnificent, inspiring edifice. It is now the tallest church in the world at 172.5 meters (566 feet). 

Pope Leo was accompanied by Cardinal Omella as he entered the basilica. Afterward, he went to the crypt to pray at the tomb of Gaudí, the man they call “God’s architect,” who died when hit by a tram on June 10, 1926. Gaudí saw nature as linked to religion, since it is the work of God; he designed this basilica with that Christian inspiration. He is now on the path to beatification.

Pope Leo, like Benedict XVI, loves music, and he surely enjoyed the musical and choral contributions at this Mass of Thanksgiving. They combined Gregorian chant, popular liturgical music, as well as choral repertoire from the Catalan tradition, the Montserrat school, and works from the great European sacred music tradition, with instrumental accompaniment of an organ and a brass ensemble. Five hundred singers from various choirs of Catalonia and 100 children from the children’s choir greatly enriched this extraordinary celebration. 

The creed and Our Father were sung in Catalan, while other parts of the Mass were said or sung, alternating in either Catalan or Spanish. 

Leo began his homily in Spanish, but sometimes spoke in Catalan, greeting the Spanish monarchs, the public authorities and the members of other Christian communities and religions who were present for “our act of thanksgiving.” 

He said the Basilica of the Sagrada Familia welcomes and invites each of us “to listen to the Word of God, which makes us a family loved by the Lord.” Indeed, he said, “all Catalonia gather in this temple, as a sign of unity and harmony for all of Spain, and lift their gaze to encounter the face of God the Father, shining forth in his Son made man, Jesus Christ.” 

He said they gathered “to give thanks to the Lord for his love toward us” and “praise him for his work in our lives.” Moreover, “we thank him in particular for this extraordinary basilica, which Pope Benedict XVI consecrated in 2010, recalling that it is a visible sign of the invisible God, for whose glory its towers rise.” 

He told them that “[m]uch more than a monument, the Basilica of the Sagrada Familia remains a work in progress today, reminding us that the Christian life is always a journey, because it is a project that God is carrying out.”

He was referring to the fact that while the 18 towers of the basilica have now been completed with the building of the Tower of Jesus Christ, the Glory facade is still being worked on; upon completion it will be the main entrance to the basilica.

Comparing our Christian life to the building, Leo said: “We do not, therefore, dwell in an unfinished work, but in a temple still under construction. The fact that it is incomplete is not a flaw, for it bears witness to a desire; it does not signify a shortcoming, but rather expresses a promise that we wish to honor with consistency.”

He said: “Our gratitude thus becomes a commitment as we cooperate in God’s plan—that is, in the edification to which he himself calls us. Since we are the temple of the Holy Spirit, this work consists in our very lives, which God conceives as a masterpiece that we are to create together, and he calls us to collaborate with him.”

Recalling the story of King David, the pope said: “Scripture teaches us that it is not we who make a dwelling for God, as if he were simply one thing among others or part of a whole greater than himself. Rather, it is God who makes a place for us, and the place he gives us is his own heart: the place of the Son,” for us who were “strangers” and “sinners.” 

He recalled the words of Jesus: “you will die in your sins unless you believe that I am he” (Jn 8:24) and said: “These are strong words, which are by no means intended as threats or blackmail. They are an invitation to salvation—that is, a call to freedom extended by Christ, who desires for us the ultimate, eternal good.”

He reminded everyone that “when faced with the threat of evil, the Lord is always with us, always on our side” and is “the source of grace and forgiveness, of salvation and new life.” 

Then in words of particular significance in the present day, Pope Leo told those present and a global audience following on television: “We cannot believe in Jesus and promote war. We cannot believe in Jesus and kill the innocent. We cannot believe in Jesus and abandon those who suffer, those who weep, those who flee from misery.”

Then referring to the Tower of Jesus Christ that he would inaugurate at the end of Mass, Pope Leo said: “Let us remember that the Cross of Christ, which crowns this Basilica, is the Cross of the last one who become the first, of sinners who become saints, of the dead who will rise again.” 

“As we admire the Tower of Jesus Christ,” he said, “we lift our gaze toward him, toward the One who alone reveals to us the truth about God and the truth about ourselves. By looking at Christ, we can see the world with renewed eyes: the tower of the cross then becomes a banner of charity, for God loves us in this way, transforming an instrument of death into a sign of hope.”

“In Jesus’ cross our faith reaches its summit,” Leo said, and noted that the cross now on top of the basilica “shines by day, reflecting the sunlight, and shines by night, illuminating the city like a lighthouse overlooking the Mediterranean.” 

He was alluding to the fact that this cross is clad in glass and some 15,000 ceramic tiles. This material is designed to shine by day in the sunlight and by night in the beams of light from the other towers, just as Gaudí wanted.

Indeed, Pope Leo said: “The light of Christ shines in the darkness, even though the darkness has not received it. Yet this rejection does not mean that God’s love is lacking.” He said: “It is necessary to pass through the passion of the crucified One to be enlightened by the glory of the risen One for from the beginning, the Father teaches us to give our lives, and the Son, who receives life from him, gives it to all through the power of the Holy Spirit. This is why the cross is the radiant sign of his love.” He added: “These are the works of faith, and art stands out among them.”

Pope Leo said that “in our prayer, therefore, we discover the original bond between all things and God, the Creator of heaven and earth. He is the Artist who has imprinted his splendor upon the cosmos. Created in his image, humanity responds to God’s work with its own ingenuity: this is how the artist transforms talent into praise and creativity into a testimony to the Creator himself.”

In this light, he said, “as an architect inspired by faith, the venerable Antoni Gaudí designed this place with the desire to narrate the mysteries of the Lord’s life. In this way, he has proposed to us a spiritual pilgrimage, leading to an encounter with Christ who for our sake was born, died and rose again.”

Pope Leo also thanked “the artists and the workers who cooperated in the construction of an architectural masterpiece, which is also an eloquent catechesis made of stones, colors and light.” 

In this way, he said, “the church renews the ‘Biblia pauperum’ [the Bible of the poor] of the ancient cathedrals, which are in themselves rich messages of evangelization” and “in this age in which image is so prevalent, it becomes even more evident how art and beauty are privileged channels of evangelization.”

The American-born missionary concluded saying: “The beauty of this church inspires us to learn ever more from our Master and Lord the art of living according to his Gospel” and “as we lift our gaze toward him, the crucified and risen One, let us commit ourselves to lifting up those who lie in the dust” and “let us show in this way that the Sagrada Familia is the tallest church in the world, not so as to stand out in worldly rankings, but rather to guide the steps of the People of God who make their pilgrimage in Catalonia, with the Cross illuminating their path, like a lamp burning brightly as we await the return of the Bridegroom.”

At the end of the Mass, Cardinal Omella thanked the pope for his visit and for promoting Pope Francis’ vision of the church as a field hospital that offers care for all. The crowd applauded warmly, and some outside the basilica shouted “viva il papa!”

In the culminating moment of this profoundly spiritual celebration, Pope Leo went outside the basilica, accompanied by Cardinal Omella and all the bishops that concelebrated with him, to bless the Tower of  Jesus Christ, on which stands the 55 feet tall cross that is visible across the city. 

In a prayer, recalling that the cross is “the mystery of mercy and salvation” and a source of life for the world, he thanked God “who enlightened your servant Antoni Gaudí to leave aside the realities of this world and seek those of heaven.” He then blessed the tower with holy water and the cross was illuminated. 

The brief ceremony ended with the singing of the sixth century hymn, “Vexilla Regis,” that is usually sung during the Passion on Holy Week and on the feast of the Exaltation of the Cross. As they sang, and the musical instruments thundered their powerful sounds, many people held lights in their hands, and the whole facade of the basilica was illuminated in a striking conclusion to this historic event. But there was more to come: a spectacular firework display across the facade of the basilica, something surely that not even Gaudi would have imagined.

Pope Leo returned to the basilica and unveiled a plaque commemorating this moment, an act that drew sustained applause. 

Thus concluded the fifth day of Pope Leo’s visit to Spain. Tomorrow morning he departs from Barcelona and takes a plane to the Canary Islands for the last two days of his visit.

Gerard O’Connell is America’s senior Vatican correspondent and author of The Election of Pope Francis: An Inside Story of the Conclave That Changed History. He has been covering the Vatican since 1985.