Some 8,000 helium balloons have been released into the night sky over Germany's capital at the culmination of events to mark the 25th anniversary of the fall of the Berlin Wall.
Earlier, Chancellor Angela Merkel said the fall of the wall had shown the world that dreams could come true.
Tens of thousands of people attended events, including a "citizen's party" at the Brandenburg Gate.
The Berlin Wall was built in 1961 to stop people fleeing the communist East.
Its fall in 1989 became a powerful symbol of the end of the Cold War.
The white balloons - perched on 3.6m poles to match the height of the wall and stretching for 15km (nine miles) - were released one by one to symbolise the breaching of the wall by crowds of protesters.
The Berlin State Orchestra under Daniel Barenboim played Beethoven's Ninth Symphony "Ode to Joy" in front of the Brandenburg Gate.
"We're the happiest people in the world and we're thrilled that you brought the Berlin Wall down 25 years ago," said the Mayor of Berlin, Klaus Wowereit, as the first balloons were sent aloft.
"Nothing and no-one can stand in the way of freedom."
The release came amid a massive open-air party at the Brandenburg Gate. Earlier at the party, UK performer Peter Gabriel sang a version of David Bowie's Heroes.
At the scene: Damian McGuinness, BBC News
For a weekend the balloons had become a part of the city, with Berliners strolling, jogging or cycling along the route.
Today not much of the Wall remains, and often you don't even notice when crossing between East and West. That's because, after 1989, Berliners wanted to destroy the much-hated barrier and rebuild their city.
But suddenly seeing the circuitous and often illogical line which tore through the city's heart was a reminder of the insanity of using concrete to split a city in two, dividing neighbourhoods, friends and families.
Now the balloons have floated off into the sky, each one accompanied by cheers from the crowd - a shining and delicate symbol of peace and light, in stark contrast to the brutality of the heavy slabs of grey concrete. And a powerful reminder of how 25 years ago, under pressure from ordinary Berliners, this deadly barrier suddenly lost its threat.
'We can change things'
The day's events began with a brass band playing, evoking the trumpets which brought down the walls of the biblical city of Jericho.
Chancellor Merkel, who grew up in East Germany, and other officials laid roses in one of the remaining sections of the wall.
Speaking at the opening of a new information centre about the Wall, Ms Merkel said it was easy to forget what had happened and it was important to remember it.
"We can change things for the better," she said. "This is the message for... Ukraine, Iraq and other places where human rights are threatened.
"The fall of the Wall showed us that dreams can come true. Nothing has to stay as it is."
Recently Ms Merkel has revealed more details about her movements on the day that the Wall opened.
She told German TV on Saturday that she joined crowds heading towards West Berlin after a visit to the sauna, describing "an incredible feeling of happiness".
The chancellor was joined later at the Brandenburg Gate by former Polish trade union leader and president Lech Walesa and Mikhail Gorbachev, the last Soviet leader.
The anniversary was also mentioned in an address by Pope Francis in Rome.
He told crowds in St Peter's Square: "Where there is a wall, there is a closing of hearts. We need bridges, not walls."
The wall stretched for 155km (96 miles) through Berlin but today only about three kilometres of it still stands.
At least 138 people died trying to flee to West Berlin.
Within a year of the wall's collapse, Germany - divided after its defeat in World War Two - was reunited.
Striking a sombre note, Mr Gorbachev, 83, warned on Saturday that the world was on the brink of a new Cold War.
Tensions between the West and Russia have been raised by the crisis in Ukraine, which was part of the Soviet Union.
"Bloodshed in Europe and the Middle East against the backdrop of a breakdown in dialogue between the major powers is of enormous concern," he said.
"The world is on the brink of a new Cold War. Some are even saying that it's already begun."
Mr Gorbachev, as leader of the USSR in the late 1980s, is credited with rapprochement with the West and creating a more liberal atmosphere which led to the collapse of communist regimes in Eastern Europe in 1989.