(CNN) -- Monday marks the 20th anniversary of the fall of the Berlin Wall, which heralded the collapse of communism in Europe and eventually an end to the Cold War.
Communist governments fell across the bloc in 1989, as populations rose against systems that had controlled them since the end of World War II.
In 1991, Russia and other Soviet republics declared their independence.
Former Soviet President Mikhail Gorbachev said the chain of events that led to the collapse began with his decision to hold competitive elections and to tell leaders of the Soviet client states that they should take charge of their own territories.
"It was the creation of a new state," he told CNN's "State of the Union" from Berlin, Germany. "In effect, pluralism, economic, political pluralism, all of that was testimony that our country was moving along the path of democracy."
World leaders including German Chancellor Angela Merkel, British Prime Minister Gordon Brown, French President Nicolas Sarkozy and Russian President Dmitry Medvedev are to attend various ceremonies Monday, marking the collapse.
More than 1,000 domino stones will line a 2-kilometer (1.2-mile) strip where the wall once stood -- a symbol of the domino effect its collapse had in ending communism throughout Eastern Europe.
Thirty of the dominos were drawn by artists in countries where there are still barriers -- Cyprus, Israel and North and South Korea.
Former CNN correspondent Richard Blystone remembers how the giant wall sliced Germany in two.
"On the west side, there was all this graffiti and dirty words, and names of rock groups and 'down with that' -- all the chaos of a pluralistic society," said Blystone, who was in Berlin the night that the wall fell.
"On the eastern side, it was clean and white, just so sterile."
Blystone said the differences became evident as the wall collapsed, as tens of thousands of East Germans pushed it down from their side, while thousands of exuberant West Germans yanked on it from theirs.
"People were pushing and pulling at the same time," he said.