With "Jesus Christ, you are my life" blaring from loudspeakers, more that 800,000 young pilgrims camped out in a muddy field were awakened early Sunday morning to prepare for the arrival of Pope Benedict XVI and the celebration of Mass.

The young people, representing nearly 200 countries, shivered in the damp morning air at Marienfeld, or Mary's Field, a former coal strip mine, as they awaited the climactic conclusion of the weeklong World Youth Day. They rolled up their sleeping bags, cleaned up their space and pulled on sweaters. Within a few hours, the field was transformed into a cheerful but soggy sanctuary filled with more than a million faithful.

As the pope approached in his popemobile, the crowd chanted his name in Italian, and waved small flags. Benedict, wearing a golden sash over his white robe, stepped out of his vehicle and mounted an altar on a small hill.

At the Mass, he urged this, the church's next generation, to wisely use the freedom God had given them.

"Freedom is not simply about enjoying life in total autonomy," he cautioned, "but rather about living by the measure of truth and goodness so that we ourselves can become true and good."

The pope stressed the importance of regularly attending Sunday Mass, saying that "if you make the effort, you will realize that this is what gives a proper focus to your free time." Church attendance across Europe has eroded steadily in recent decades.

During his closing homily, Benedict said that there was a "strange forgetfulness of God," while at same time the sense of frustration and dissatisfaction has led to a "new explosion of religion."

"I have no wish to discredit all the manifestations of this phenomenon," he said. "Yet, if it is pushed too far, religion becomes almost a consumer product. People choose what they like, and some are even able to make a profit from it."

"But religion constructed on a 'do-it-yourself' basis cannot ultimately help us," he said.

Sunday was the last day of the pope's first international trip, a four-day visit that took the German-born pontiff back home. During his stay, Benedict visited a synagogue, becoming only the second pope to do so, and warned about rising anti-Semitism. He later met with Muslim leaders, delivering a strong rebuke of terrorism and asking Muslims to join Christians in trying to combat its spread and "turn back the wave of cruel fanaticism" behind it.

In his farewell remarks at the airport before leaving Germany on Sunday night, the pope said he hoped people had seen another Germany that would counter the shameful memory of Nazi rule and World War II. The pope revealed in a memoir that in 1941, he served against his will in Adolf Hitler's Nazi youth movement and later was drafted into a Nazi antiaircraft unit.

"During these days, thanks be to God, it has become quite evident that there was and is another Germany, a land of singular human, cultural and spiritual resources," he said, the Associated Press reported.

Many young people expressed disappointment that they had not been given more opportunities to meet with the pope outside of Mass.

"He could have spent a little more time with us young people," said Michael Benner, 16, who attends a private school run by Benedictine monks in Marienstatt, a few hours to southeast of Cologne. "It was important to visit the synagogue, but some of the other visits could have been next time. He's supposed to be here for the World Youth Day, and it's for us young people."

Michael's classmate, Linda Neurath, also 16, said "this unique experience with so many people who came such a distance to see the pope, to show they believe" had left her exhilarated.

Comparisons were rife between Benedict, who has a reputation for being reserved and media-shy, and his charismatic predecessor, John Paul II, who died in April. John Paul, who founded World Youth Day in 1984, was known for his openness and frequent international travel.

But many of the people assembled Sunday said Benedict had dazzled them with his enthusiasm and joyful spirit.

"I listened to what he was saying and thought, man, he is better than I thought! I didn't expect to be moved by him," said Stefan Bauer, 24, a student from Munich.

The pope leaves the World Youth Day festival held outside Cologne. People from nearly 200 nations celebrated with him on his first trip abroad as head of the Roman Catholic Church.Benedict arrives in his bullet-proof popemobile to say Mass at the end of his visit to Germany.