The Berlin Wall fell in:

The Berlin Wall fell on 9 November 1989, marking one of the most significant events of the 20th century and symbolising the end of the Cold War division of Europe.

The Berlin Wall had been erected by the East German government in August 1961 to prevent East Germans from fleeing to West Berlin and, by extension, to West Germany and the Western world. For 28 years, the Wall stood as the most visible symbol of the Iron Curtain dividing communist Eastern Europe from democratic Western Europe.

By 1989, political and economic reforms sweeping across Eastern Europe - partly inspired by Soviet leader Mikhail Gorbachev's policies of glasnost (openness) and perestroika (restructuring) - weakened communist regimes across the region. Mass protests in East Germany, combined with Hungary opening its border with Austria (allowing East Germans to flee westward), created irresistible pressure. On 9 November 1989, the East German government announced that citizens could cross the border freely. Crowds of East and West Berliners began dismantling the Wall that same night.

The year 1990 saw German reunification (3 October 1990), which followed the Wall's fall. The year 1991 marked the dissolution of the Soviet Union. The year 1987 predates these events, though it was when President Reagan made his famous "tear down this wall" speech.

The correct answer is 1989, the year the Berlin Wall fell.