Hundreds of thousands of young people gathered Thursday in the Spanish capital's Plaza de Cibeles to welcome Pope Benedict XVI to the 26th World Youth Day celebration, which has drawn young people from 193 countries.

Defying the high summer temperatures in Madrid, the festive crowd of singing, flag-waving youth greeted the pope like a pop star.

After making his entrance at the 2005 WYD in Cologne, Germany, along the Rhine River and in Sydney, Australia, in 2008 at the city's world famous harbor, the pope arrived at the celebration in Madrid on foot through the historic Puerta de Alcala in the heart of the capital.

Fifty youth, 10 from each continent, accompanied the head of the Catholic Church as he walked through the Neo-classical monument in Madrid's Independence Square.

He later planted an olive tree - in keeping with the slogan of this year's WYD, "Rooted and built up in Jesus Christ, Firm in the Faith" - and then climbed aboard the popemobile for the ride to the nearby Plaza de Cibeles, a massive square that is one of Madrid's most famous landmarks.

There, amid the cheers from the vast crowd of young people, Madrid Archbishop Antonio Maria Rouco Varela officially welcomed Benedict XVI to the city, "where no one is a stranger, but rather a brother."

"It's with great joy that I find myself here with you in the center of this beautiful city of Madrid, which today is also the capital of the world's youth," the pope said at the start of his four-day visit.

Benedict XVI called for Christ's message of hope to "resound" throughout all corners of Madrid "and also echo in the hearts of those who do not believe or who have distanced themselves from the church."

While traveling from Rome to Madrid, Benedict XVI expressed concern over the economic crisis and, in a conversation with reporters accompanying him, referred to the large numbers of jobless youth in Spain, where the unemployment rate is more than 20 percent.

The economic crisis is also a crisis of ethics, he said, adding that human beings must be at the center of the economy and not the reverse.

And upon his arrival in Madrid, his first words were directed toward young people as well as to recall Spain's Christian roots.

The pope also denounced the "harassment and disdain" suffered by Christians in many parts of the world, especially in the increasingly secularized West, where the goal appears to be to "silence" the Catholic faith and even the name of Christ.

The 84-year-old pontiff urged young Christians not to be afraid and not to be "ashamed" of Christ and warned about the "superficiality, consumerism and hedonism" of the modern world.

Benedict XVI, who was welcomed to Spain by King Juan Carlos and Queen Sofia, as well as by Prime Minister Jose Luis Rodriguez Zapatero, said he was thrilled to travel to the country for the third time.

He said he "admires" Spain for its rich history and culture and the vitality of its faith, evidenced by the many saints through the years and the numerous men and women who left their homeland to bring the Gospel to all corners of the globe.

World Youth Day is an event to celebrate the Catholic faith that is organized internationally once every two or three years in different parts of the world.