Benedict XVI has returned to his native Germany for his first major foreign trip since being elected pope in April.
He is in Cologne to honour a vow made by John Paul II to attend the Catholic World Youth Festival.
Hundreds of thousands of pilgrims are in the city for the week-long festival.
The Pope visited German President Horst Koehler at the presidential residence in the former German capital, Bonn.
The president's wife, Eva, looked on as the pontiff signed the villa's visitor guest book, known as the 'golden book'.
Then Benedict XVI became only the second Pope in history to enter a Jewish place of worship, as he joined Jewish leaders at Cologne's main synagogue.
There he made a speech denouncing the Holocaust and warning against the threat of new anti-Semitism.
Souvenir merchants were on hand to offer mementos of the historic occasion.
Pope Benedict has also used his trip to meet Germany's Muslim leaders in Cologne.
And he reached out to 700,000 pilgrims at an open-air prayer vigil at a park outside the city.