The giant service at a former coal mine outside Cologne was the final major public appearance of Benedict's first foreign trip as pope, a trip which had been planned for Pope John Paul II.

But despite a more retiring nature than his charismatic predecessor, the 78-year-old German appeared to have won over the massive crowd, most of whom spent a damp and chilly night at the site to await his return after a prayer vigil in the same location on Saturday as the World Youth Day jamboree built up to its finale.

Pilgrims from all over the world had spent the night at the site where the mass was held. Some 700,000 had attended a prayer-vigil with Benedict the night before, but the World Youth Day organizers said the numbers had swelled to "more than one million" by Sunday's mass.

Though shy and retiring, and lacking the forceful personality of his predecessor John Paul II who reveled in such occasions, Benedict appears to have turned a corner in his pontificate and embellished his once rather dry appeal to young people with his first foreign trip.

The young crowd gave Benedict a noisy reception under a huge canopy of swirling flags when he arrived aboard his popemobile, waving and blessing the crowd.

With the roads criss-crossing the site blocked by pilgrims standing to get a glimpse of the mass on giant television screens, Benedict apologized for not being able to tour through the faithful in his popemobile.

Pope calls for mass to become part of youth's lives

"I would like to have been able to go through the crowd and greet each and every one of you. That was not possible, but I greet you warmly," he said.

At one point, the pope cajoled them like a grandfather, gently urging them to "make the effort" to attend Sunday mass.

"Dear friends, sometimes our initial impression is that having to include time for mass on a Sunday is rather inconvenient. But if you make the effort, you will realize that this is what gives a proper focus to your free time."

Benedict urged the young Catholics to keep God at the centre of their lives and underlined the importance of Sunday mass and receiving Holy Communion.

And the huge crowd seemed to appreciate the pope's gently-delivered message, which sought to convey his own burning enthusiasm for the deeper mysteries of faith and the mass.

"He seemed a lot younger and more vibrant than we had expected," said George Pierce, 17, from the US state of Pennsylvania. "Having heard his homily, I have a much better understanding of him and of his past. I feel I have got to know him."

Unusually for a pope, he even used the phrase "nuclear fission" to describe the spiritual effect of receiving Holy Communion, in which Catholics believe bread and wine blessed by a priest is turned into the body and blood of Christ in imitation of the Last Supper.

Massive crowd made personal contact impossible

An overcast and breezy day in Cologne broke into glorious sunshine as the pope began his homily. Calling on the pilgrims and visitors to World Youth Day to make wise use of the freedom God had given them, Benedict said, "Freedom is not simply about enjoying life in total autonomy, but rather about living by the measure of truth and goodness so that we ourselves can become true and good."

"Explosion" of religion in difficult times

The pope added that in these modern times there was a "strange forgetfulness of God," while at same time the sense of frustration and dissatisfaction had led to a "new explosion of religion."

"If it is pushed too far, religion becomes almost a consumer product," he said. "Help people to discover the true star which points out the way to us: Jesus Christ."

He announced at the ened of the mass that Sydney, Australia, would host the next World Youth Day in 2008.

Benedict was due to return to Rome on Sunday evening at the end of what is being seen as a highly successful visit during which he met also met German Jewish and Muslim leaders.

In a landmark visit to Cologne's synagogue on Friday -- only the second ever by a pope to a Jewish place of worship -- he condemned the "unimaginable crime" of the Holocaust in an address to Jewish leaders.

And on Saturday he urged Muslim leaders to do more to combat the "cruel fanaticism" of terrorism that aimed to poison ties between Christians and Muslims.

Disclaimer: Deutsche Welle is a media partner of World Youth Day 2005.