COLOGNE, Germany — Pope Benedict XVI yesterday paid only the second visit to a synagogue by a Roman Catholic pontiff, decrying "the insane, racist ideology" practiced by his fellow Germans that led to the Holocaust and World War II.

Benedict, a conscripted teenage member of the Hitler Youth who was also forced to join the German military during the waning days of the war, memorialized the 6 million Jews who died in the Holocaust, visiting a synagogue that was destroyed by the Nazis in 1938 but rebuilt two decades later.

"The holiness of God was no longer recognized, and consequently contempt was shown for the sacredness of human life," Benedict said. He quoted his predecessor, John Paul II, who said memories of the Holocaust must "never cease to rouse consciences, to resolve conflicts, to inspire the building of peace."

The pope continues his outreach to leaders of other faiths today in a meeting with Muslim leaders in Cologne, where he was spending four days to attend the church's 20th World Youth Day. He is scheduled to celebrate Mass for several hundred thousand people tomorrow, the last day of his trip.

Catholic and Jewish leaders described Benedict's visit to the Cologne synagogue as an important milestone in relations between Jews and Catholics, which improved considerably during John Paul's 27-year reign but have suffered some setbacks in recent months. They said the mere presence of a German pope — the first in 500 years — in a synagogue was something they could not have imagined.

"This was an event that not only has exceptional meaning for Germany, not only for the Catholic Church, but also for the Jewish community in Germany and in the world," said Paul Spiegel, director of the German Jewish Council. "It is a historic day, an event that will be thankfully remembered by future generations."

Upon entering the Jewish house of worship, Benedict stopped to pray briefly at a memorial to Jews who died in the Holocaust, including about 11,000 from Cologne, which served as an important European center of Jewish learning and culture from the 4th century until the Nazis decimated the community.

While Benedict spoke of the common theological ground between the Jewish and Catholic faiths, he did not apologize for the church's failure to take a stronger public stand against the Nazis during World War II and the Holocaust, as many Jewish leaders have urged the Vatican to do in recent years.

Abraham Lehrer, a Jewish community leader in Cologne, asked Benedict during the synagogue visit to further open the Vatican's World War II archives to detail the church's response to the Holocaust. Such a gesture "would be a further sign of historical conscience and would also satisfy critics," Lehrer said during the ceremony.

Benedict did not respond directly. But he made a general reference to such disputes, saying he "would encourage sincere and trustful dialogue between Jews and Christians, for only in this way will it be possible to arrive at a shared interpretation of disputed historical questions."

Vatican officials portrayed the synagogue visit as Benedict's idea. Joaquin Navarro-Valls, the papal spokesman, said it was "an event of historic significance" and emphasized that the pope "himself took the initiative and said he wanted to visit the synagogue."

Lehrer said, however, that Cologne's Jewish community board of directors had taken the first step. He said the board decided shortly after John Paul's death in April to send a congratulatory letter and invitation to whoever would be named his successor, realizing that the new pope was likely to visit Cologne this month to attend the previously scheduled Catholic world youth summit.

"We decided, well, we're going to invite whoever the winner is and we'll see what will happen," Lehrer said. He said the Vatican responded eagerly soon after Benedict's election, formally accepting the invitation in June.

Special correspondent Shannon Smiley contributed to this report.