Brief Summary
The Set-Up
President Kennedy was sightseeing in West Berlin when he stopped to give a pep talk to a crowd of Berliners who'd been getting the wrong end of the Cold War lollypop.
The Text
After name-dropping a few people that the Berliners knew and liked, Kennedy digs out a rusty old Latin saying and updates it, in German, applying it to Berlin. With the crowd now firmly on his side, Kennedy challenges anyone who doesn't think that communism is bad news to take a good look at Berlin, which is basically half communist/half free…with an unfortunate wall separating the two.
He continues sucking-up to Berliners by praising their resilience while at the same time badmouthing the illogical reasons for the wall and the whole system of communism.
Kennedy then begins to wrap things up by suggesting that even though Berlin's gone through a lot of bad stuff recently for a long time, the whole world is watching and someday Germany will be reunited. He ends by explaining how everyone is connected through some magic cosmic force (that he doesn't really take the time to explain except that it makes us all citizens of Berlin).
TL;DR
The communists may have broken the city of Berlin, but they can never break the spirit of the people who live there.