Germany is celebrating 25 years since the fall of the Berlin Wall, a milestone in ending the Cold War, by throwing a huge open-air street party at the iconic Brandenburg Gate.

More than a million people are expected in the reunited capital to see rock stars and anti-communist dissidents take to the stage amid fireworks displays to recall the peaceful breach of the despised concrete barrier.

The ugly scar the Wall once cut through Berlin has been marked by an art installation, a string of almost 7,000 illuminated white balloons tethered along a 15-kilometre stretch of its former 155-kilometre path.

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To symbolise the tumultuous day the barrier first cracked open on November 9, 1989, the balloons will float into the sky at dusk to the stirring strains of Beethoven’s Ode to Joy, the anthem of the European Union.

Later the unofficial Wall anthem Heroes, which David Bowie recorded in a studio near the barrier in then-West Berlin, will ring out across the city, performed by British singer-songwriter Peter Gabriel.

The anniversary celebrations started on a sombre note with a church service and ceremonies for the at least 389 victims of the border, who were shot, blown up by mines or otherwise killed as they tried to escape the East.

German Chancellor Angela Merkel and Berlin mayor Klaus Wowereit place flowers in the wall. Photo: AAP

Chancellor Angela Merkel, 60, who grew up a pastor’s daughter under communism, joined other dignitaries at a memorial at Bernauer Strasse, which saw harrowing scenes of people jumping from windows when the Wall first went up in 1961.

“It took a long time and many people’s suffering to make it possible for the Wall to fall, not just in Germany but also in Poland, Hungary, Czechoslovakia and many other countries,” Merkel told reporters at the event.

“That’s something we should remember on a day like today.”

Unlike the 20th anniversary celebrations, when many heads of state and government flocked to Berlin, this time around the festivities are mainly a people’s celebration in a city that has blossomed into a cultural hub and major European tourist destination.

More than a million people were expected to descend on Berlin over the weekend, said tourism group Visit Berlin.

One visitor who walked along the Wall light installation – called Lichtgrenze or light frontier – was Benjamin Nemerofsky, 41, a Canadian artist who has lived in the city since 2001.

“The fall of the Wall changed many things in Europe, in Germany and in Berlin,” he said.

“This is a city where you can see 20th century history at every corner. That’s fascinating,” he said.

The ‘Border of Light’ seen from the air. Photo: Twitter

The only foreign dignitaries are veterans of the era, chiefly the last Soviet leader, Mikhail Gorbachev, 83, whose “glasnost” and “perestroika” reforms kicked off the series of historic events which led to the Wall coming down.

Gorbachev – who remains highly popular in Germany – warned on Saturday that the world was on the “brink of a new Cold War”, amid East-West tensions over Ukraine.

Also at the festivities will be Polish freedom icon Lech Walesa, 71, Hungarian ex-premier Miklos Nemeth, 66, and German President Joachim Gauck, 74, a former Christian pastor and rights activist in the East.

East Germany built the Wall, which it dubbed its “Anti-Fascist Protection Rampart”, in August 1961 to halt a mass exodus of citizens to the West. First described as temporary, the Wall stayed for 28 years.

-AAP