Berliners sing and dance on top of the Berlin Wall to celebrate the opening of East-West German borders, Friday afternoon, Nov. 10, 1989. Thousands of East German citizens moved into the West after East German authorities opened all border crossing points to the West. In the background is the Brandenburg Gate. Built in 1961 of barbed wire and concrete, the wall divided Berlin, becoming the most powerful symbol of The Cold War. It prevented East Germans from freely traveling or migrating to the West. The two nations were reunited as a single country, 45 years after World War II on Oct. 23, 1990. The change -- Die Wende -- or reunification, created one of the world's strongest economies in the 20th century.