Pope Benedict XVI has become the second leader of the Roman Catholic Church to visit a Jewish temple. Speaking at a synagogue in Cologne, Germany Friday, he said Christians and Jews must work together to ensure that the "insane racist ideology" that led to the Holocaust never occurs again. He also warned of rising anti-semitism and hostility against foreigners.

As the choir sang Shalom Aleichem, the pope walked into the main hall of the synagogue in Cologne. It was the second time a leader of the Roman Catholic church has visited a Jewish temple. Pope John Paul II visited the Rome synagogue in 1986.

First, Pope Benedict stood in front of a memorial to the millions of victims of the Holocaust. Then a ram's horn was sounded and the pope sat in front of the congregation listening carefully as the rabbi said his visit was a step towards peace between peoples of the world.

Pope Benedict said it was his deep desire, on his first visit to Germany since his election last April, to meet the Jewish community. He acknowledged that the history of relations between Jewish and Christian communities has been complex and often painful.

Then he referred to the darkest period of German and European history, when, an "insane racist ideology" led to the Holocaust, which he referred to as an "unspeakable and previously unthinkable crime."

Pope Benedict XVI said the terrible events of that time must never cease to rouse consciences, to resolve conflicts and to inspire the building of peace.

In his speech, the pope also warned that today "we are witnessing new signs of anti-Semitism and various forms of general hostility towards foreigners." He said there is a need to be vigilant. And reaffirmed that the Catholic Church is committed to tolerance, respect, friendship and peace between peoples, cultures and religion.

Pope Benedict said much progress has been made in relations between Jews and Christians, adding that efforts along this path must continue.

"Much still remains to be done," he said. "We must come to know one another much more and much better." He encouraged sincere and open dialogue between Jews and Christians.

At the end of the pope's speech, the congregation stood and gave him lengthy applause. Earlier, addressing the pope, one of the Jewish community's leaders, Abraham Lehrer, urged the pontiff to open the Vatican's historical archives for the wartime period.

Pope Benedict's visit to a Jewish temple so early in his papacy, was a sign of continuity with his predecessor and showed just how much relations between the two communities have improved in Germany.

The synagogue he visited Friday was destroyed by the Nazis during the anti-Jewish Crystal Night riots in 1938 and then rebuilt more than 20 years later. Today it is one of the largest synagogues in Germany and is home to the oldest Jewish community in the country.