Pope Benedict held the final Mass of his four-day visit to Spain Sunday and urged some 1.5 million young Catholics to spread the gospel and avoid trying to find faith on their own.

The pontiff encouraged pilgrims from 193 nations, who gathered in Madrid for the World Youth Day, to do so even if they are met with rejection or indifference. He also announced that the next youth festival will be held in Rio de Janeiro, Brazil, in 2013.

The open-air Mass, conducted in Spanish, was attended by Spain's King Juan Carlos and Queen Sofia. Before leaving for Rome late Sunday, Benedict held a farewell ceremony at Madrid's Barajas airport. He said Spain, which has ushered in fast-track divorce and easier access to abortion and gay marriage, should hold on to its Catholic soul.

“Spain is a great nation whose soundly open, pluralistic and respectful society is capable of moving forward without surrendering its profoundly religious and Catholic soul,” the pontiff said.

The World Youth Day was marked by a violent storm, blistering heat and protests. Organizers said many pilgrims could not receive the sacrament of Holy Communion during the Mass because gusts of wind had damaged several tent chapels and police sealed them as a safety precaution.

Benedict held a prayer vigil Saturday evening at the Cuatro Vientos airport near Madrid, but a violent thunderstorm forced the pontiff to cut short his speech. He thanked the gatherers for their “joy and endurance,” saying their strength was “greater than the rain.”

Earlier in the day, firefighters had sprayed the crowds with water from hoses in a bid to stave off the near 40-degree heat.

This was the pontiff's third World Youth Day. The first such event was launched a quarter century ago by Pope John Paul in a bid to reinvigorate and spread the faith among the young.