Berlin is celebrating the 40th anniversary of John F Kennedy's "Ich bin ein Berliner" speech, which he delivered as a message of solidarity to West Berlin at the height of the Cold War.
US-German relations have diverged since the visit
To mark the anniversary, the speech itself was replayed on Thursday over the loudspeakers from the town hall in Schoeneberg, where it was made.
In what even now was an emotional moment, hundreds of people came to cheer and wave the American flag, including some Berliners who were here in 1963.
Earlier, German President Johannes Rau wrote in an open letter to his US counterpart George W Bush that the speech had become a "milestone of German history and a solid anchor for US-German friendship".
"I want to thank you, Mr President, and the American people, for extending the hand of friendship to us - a friendship for which Kennedy created a lasting symbol 40 years ago and which has stood the test of time ever since," the letter reads.
Mr Rau added that US-German relations had flourished in the past because they were based on mutual respect and that this was possible in the future as well.
The BBC's Ray Furlong in Berlin says the Kennedy speech was perhaps the most famous single moment of the Cold War.
More than a million West Berliners gathered to hear it in June 1963, and they responded to it with a great roar of approval.
Now advertising hoardings across the city are promoting a new exhibition at the German Historical Museum - originally an East German institution dedicated to promoting the Communist world view.
LANDMARKS OF POST-WAR US-GERMAN RELATIONS
1947 - Marshall Plan for economic revival
1949 - Berlin airlift
1963 - Kennedy visit
1987 - Ronald Reagan calls on Mikhail Gorbachev to tear down the wall
German Foreign Minister Joschka Fischer, opening the exhibition, described Kennedy as a "thrilling" leader who combined resolve with a search for peace.
He said that the relationship between the two countries had survived differences in the past.
But the anniversary comes at a time when relations between Germany and America have changed.
With the Cold War over, their interests have diverged. The last time current President George W Bush visited Berlin, he was met with the banner: "You are no Berliner."
Our correspondent says that with the bitter rift over Iraq still not healed, there is little prospect of him coming again soon.