"Tear Down This Wall" 

In perhaps the most dramatic appearance of his Presidency, Reagan traveled to the Brandenburg Gate at the Berlin Wall and challenged "General Secretary Gorbachev" to "tear down this wall" separating West Berlin from the Soviet-backed eastern part of the city. Few would have guessed, barely two years later, the wall would fall, foreshadowing the Soviet Union's 1991 collapse.
Source: C-SPAN3: "President Reagan at the Berlin Wall" ( • President Ronald Reaga... .