Germany has launched three days of celebrations under the banner "Courage for Freedom" to mark the 25th anniversary of the fall of the Berlin Wall.
The festivities are remembering the peaceful revolution that led East German border guards to open the gates to West Berlin on November 9, 1989, allowing free passage to large crowds. The East German authorities had built the Berlin Wall in August 1961 to halt a mass exodus to the West.
Germany reunited the following year, on October 3, 1990.
Nearly 7,000 white balloons pegged to the ground along a 15-kilometre stretch of the Berlin Wall were illuminated at dusk on November 7.
Mikhail Gorbachev, the Soviet leader whose "perestroika" and "glasnost" reforms helped pave the way for the changes, greeted crowds at Berlin's former Checkpoint Charlie border crossing.
Speaking amid East-West tensions over the Ukraine crisis, he said the collapse of the Berlin Wall demonstrates how important good relations between Germany and Russia are for the entire world:
"We have learned from the past that when Russians and Germans understand each other ... when our relationship is good, then everyone is well off, not just our two peoples," Gorbachev said.
The 83-year-old former Soviet leader added that "we must make sure that we get the tensions that have arisen recently under control."
In a recent podcast, German Chancellor Angela Merkel, who was born in 1954 and grew up in communist East Germany, said she will "never forget" November 9, 1989 because she "had to wait 35 years for that feeling of liberty."
WATCH: When The Berlin Wall Tumbled In 1989 (natural sound)
On November 8, Merkel will attend a concert at the Berliner Ensemble theatre opposite the former Palace of Tears, where Easterners said goodbye to visitors returning to West Germany.
And on November 9, she will open an exhibition on the once divided Bernauer Strasse.
Celebrations will conclude at the Brandenburg Gate, the symbol of German unity, to mark exactly 25 years since Germany's Cold War divisions were breached 25 years ago.
There, Gorbachev and former Polish president and freedom icon Lech Walesa, will join German head of state Joachim Gauck, a former pastor and rights activist in the East, and Hungarian ex-premier Miklos Nemeth.
Later, rock stars and veteran freedom activists will join a crowd expected to number in the millions for a giant festival.