BERLIN (AP) -- Tens of thousands of people celebrated the fall of the Berlin Wall 35 years ago in Germany's capital on Saturday with open-air concerts, art installations and official events commemorating one of the country's most historic days on Nov. 9, 1989.

It was "a lucky day for which we Germans are still grateful today," Chancellor Olaf Scholz said.

Built in 1961, the Berlin Wall stood for 28 years at the front line of the Cold War between the Americans and the Soviets. It was built by communists to cut off East Germans from the supposed ideological contamination of the West and to stem the tide of people fleeing East Germany.

It had carved a 156.4-kilometer (97.2-mile) swath through Berlin's heart and the surrounding countryside, and through the hearts of many of its people. However, when the border was opened 35 years ago, it took less than a year until the country's reunification on Oct. 3, 1990.

Today only a few stretches of the wall remain, mostly as a tourist attraction.

For the anniversary celebrations on Saturday, event organizers created a temporary wall of 5,000 posters designed by children and adults under the motto "We uphold freedom," which attracted a steady flow of visitors, including many foreign tourists. It stands along a four-kilometer (2.5-mile ) stretch of the former wall in downtown Berlin.

The posters combine the demands of East German protesters against the communist authorities in autumn 1989, such as freedom of expression, freedom of the press and freedom to travel, with current day wishes and were created as part of workshops in schools, church parishes, local art groups and cultural projects.

"Uphold freedom, because without freedom everything else is nothing," Berlin Mayor Kai Wegner said at an official anniversary event with President Frank-Walter Steinmeier at the Berlin Wall Memorial.

"Freedom and democracy have never been a matter of course," the mayor said, warning that both were currently under attack from many sides.

For Saturday night, 700 professional and amateur musicians were expected to synchronously play songs on different stages along the path of the former wall.

Among other songs, they were planning to perform Heroes" by David Bowie and "Freiheit," or freedom, by German rockstar Marius Muller-Westernhagen. The lyrics will be shown on screens so that the audience can sing along.

The Russian dissident band "Pussy Riot" is expected to perform on Sunday as the highlight and conclusion of the anniversary celebrations.