COLOGNE, Germany - Pope Benedict XVI urged Europe to rediscover its Christian tradition and warned against rising secularism as he concluded his first foreign trip with an open-air Mass for a million people in his native Germany.

The four-day trip underlined interfaith relations - also a key theme of John Paul II's papacy. Benedict visited a synagogue in which he won applause for his warning about rising anti-Semitism, and he had a frank talk with Muslims about terrorism.

The 78-year-old pope on Sunday called on the pilgrims attending the World Youth Day Festival in Cologne to wisely use the freedom God gave them.

"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," he told the crowd.

The throngs from almost 200 countries had been invited to the festival by a different pope, the charismatic John Paul, before his death April 2.

But they embraced his more subdued successor with the same huge turnout, shouts and applause on his first foreign trip as pope.

"Beeen-e-DET-to, Beeen-e-DET-to," they chanted, using the Italian version of his name. Some 800,000 of them spent the night in the Marienfeld, or Mary's Field, outside Cologne, sleeping on the ground so they could attend Sunday's mass.

Benedict returned to Rome Sunday night.

The pope used his trip to make it clear that he intends to continue key parts of John Paul's heritage. In particular, he held two important interfaith meetings with Muslims and Jews. He became only the second pope in history to visit a synagogue when he spoke to Cologne's Jewish community, winning a standing ovation for his warning of rising anti-Semitism.

He made blunter statements during a meeting with Muslim officials, addressing them as "my dear Muslim friends" but raising the issue of terrorism, which he called "cruel fanaticism."

Yet it was clear he was establishing his own style. There were none of John Paul II's theatrical gestures such as kissing the ground on arrival or shuffling to the music. Instead, he read his speeches slowly in a soft voice and waved and smiled shyly at the loud applause that greeted him every time he came out in public.