Hundreds of thousands of sweltering pilgrims crammed into central Madrid for a giant open-air mass Tuesday, launching a million-strong, six-day Catholic youth party for Pope Benedict XVI.
Youngsters poured into the city centre for a rock-festival style celebration of World Youth Day, drawing faithful from 193 nations but also criticism in the midst of Spain's economic hardship.
From a vast white stage adorned with an image of Mary and Jesus in the emblematic Plaza Cibeles square, Madrid's archbishop, Cardinal Antonio Maria Rouco Varela, celebrated the inaugural Mass.
Some 800 bishops, archbishops and cardinals from around the world joined him, along with 8,000 priests who co-celebrated the mass.
The service includes a eucharist dedicated to the late pope John Paul II, who started the festival in 1986 as a way to revitalize the faith among young Catholics.
Before the mass, pop music blared out from dozens of massive speakers in the city centre as young pilgrims, many wearing yellow World Youth Day T-shirts and floppy hats, gathered in 35-degree C (95 F) temperatures or sat on the grass on the Paseo de Recoletos avenue.
The Church also opened 200 white confessionals in the form of boat sails along the main thoroughfare through Madrid's Retiro park, where priests and bishops from across the world listened -- in 30 languages -- to the confessions of the pilgrims.
The 84-year-old pontiff, spiritual leader to the Roman Catholic Church's claimed 1.2 billion followers, arrives Thursday to join the final four days of the party.
The 50.5-million-euro ($73-million) cost of staging the event, excluding security measures, has sparked howls of protest in a country tightening its belt and suffering a youth jobless rate of over 45 percent.
Church officials say most of the cost will be covered by the pilgrims themselves, who pay a registration fee, and the celebration will be a massive tourist boost for Spain.
But more than 100 groups that oppose the pope's visit plan to protest Wednesday on the eve of his arrival. They include groups representing gays and lesbians, feminists as well as leftist political parties.
Many of those in the country's 15-M "indignant" movement -- launched on May 15 against the management of the economic crisis, soaring unemployment and political corruption -- are also taking part.
"It is an abuse, stupidity, because they occupy the squares for several days," said 78-year-old retired Spanish and English language professor Amadeo Alaez in central Madrid.
"But on the other hand it is tourism, folklore, people have fun, the youngsters dance and have a good time because they are on holiday."
Benedict arrives to a grand welcoming ceremony in Cibeles square on Thursday.
Then on Friday he presides over a 700-metre-long (nearly half-mile) Stations of the Cross, a Church service representing the steps in Jesus' crucifixion and resurrection.
Some 15 religious treasures from around Spain will be displayed along the route on the Paseo de Recoletos.
On Saturday, hundreds of thousands of believers will be entertained by pop groups at the Cuatro Vientos air base southwest of the capital. The pope will hold a "Prayer Vigil" at the base in the evening.
The young pilgrims will then spend the night under the stars at the base with duvets and rugs on a vast esplanade the size of 48 football pitches, hoping it does not rain.
The Pope celebrates Mass there on Sunday morning at a white altar almost 200 metres (660 feet) long in front of a wave-shaped stage and under a giant parasol "tree", made of interwoven golden rods that will protect him from Madrid's brutal August heat.
Benedict last visited Spain in November 2010 for a trip in which he railed against social reforms introduced by Spain's Socialist government such as same-sex marriage, easier access to abortion and fast-track divorce.