Germany hosted European leaders at a commemoration on Saturday marking the 30th anniversary of the fall of the Berlin wall, a historical turning point that Europe and the world.
After a full week of remembrance, leaders from Slovakia, Poland, the Czech Republic and Hungary came to Berlin.
German President Frank-Walter Steinmeier thanked Eastern European neighbours for enabling a peaceful revolution.
"Together with our friends, we remember with deep gratitude the events 30 years ago," Steinmeier said during a ceremony at the Bernauer Strasse Berlin Wall Memorial, which was also attended by Chancellor Angela Merkel and heads of state from Poland, Hungary, Slovakia and the Czech Republic.
"Without the courage and the will to freedom of the Poles and Hungarians, the Czechs and Slovaks, the peaceful revolutions in Eastern Europe and Germany's reunification would not have been possible," Steinmeier said.
An emblem of the Cold War and separation of the West and the East, the Berlin Wall was not demolished immediately.
Its demolition started on 9 November 1989, with people chipping it off with hammers, chisels and sledgehammers, creating unofficial border crossings and symbolically ending decades of geopolitical tension.
The reunification of East and West Germany was made official on October 3, 1990.
During the ceremony, Steinmeier and the presidents of Poland, Hungary, Slovakia and the Czech Republic placed roses in a small gap in the remains of the wall at the memorial.
In August 1989, Hungarian border guards for the first time allowed people from East Germany to cross freely into Austria, paving the way for the fall of the Berlin Wall three months later and with it the end of the Iron Curtain.
Steinmeier pointed out, however, that the historic event did not mark the "end of history" as US historian Francis Fukuyama stated. The struggle of political systems had continued and the future was more uncertain than ever before, he added.
"Liberal democracy is being challenged and questioned," Steinmeier said. That's why Germany and its European allies had to fight every day for a peaceful and united Europe with each country having to do its part to overcome differences, he added.
His message was echoed by Merkel in a brief speech during a commemorative service at the memorial's chapel.
"The values on which Europe is founded -- freedom, democracy, equality, the rule of law, respect for human rights --are anything but self-evident. And they have to be filled with life and must be defended again and again," she said.
Celebrations will culminate this evening at the Brandenburg Gate on a large stage show, where the Staatskapelle, conducted by Daniel Barenboim, will open the festivities.
Click on the player above to watch the commemorations.