BERLIN — Ulrich Sauff and his wife stared at the mammoth domino pieces marking the path where the Berlin Wall once stood and reminisced about life in the barrier's shadow.
"It was like a prison," said Sauff, 73, who lived on the Western side of the wall. "For us 'Wessis,' the few kilometers from our old home to our new home (in the East) was unthinkable."
The Sauffs were among those who gathered Monday to celebrate 20 years of unity, marking the day the wall came down. Thousands cheered as 1,000 colorfully decorated dominoes along a mile-long route were toppled to symbolize both the moment the wall came crashing down and the resulting fall of communist governments in Eastern Europe.
It was the finale to a day of memorial services, speeches and events that attracted leaders from around the world, including former Soviet leader Mikhail Gorbachev.
Chancellor Angela Merkel and 78-year-old Gorbachev stood shoulder to shoulder as they crossed a former fortified border crossing point between East and West Berlin to cheers of "Gorby! Gorby!"
"Looking back, we can see many causes that led to the peaceful revolution, but it still remains a miracle," German President Horst Koehler told the leaders of all 27 European Union countries, Russian President Dmitry Medvedev and Secretary of State Hillary Rodham Clinton.
Merkel – Germany's first chancellor to be raised in the former communist East – called the events of Nov. 9, 1989 an "epic" moment in history.
"For me, it was one of the happiest moments of my life," Merkel told a crowd of tens of thousands packed around the Brandenburg Gate.
In a video message screened at the main event, President Barack Obama paid tribute to the dissidents and demonstrators who ushered in the fall of the wall 20 years ago.
"Let us never forget Nov. 9, 1989, nor the sacrifices that made it possible," Obama said to applause and cheers.
Clinton paid tribute to Germany and other countries who shook loose communist bonds.
"We remember the people of the Baltics who joined hands across their land ... we remember the students of Prague who propelled a dissident playwright from a jail cell to the presidency," she said. "And tonight we remember the Germans, and especially the Germans in the East who stood up to say 'No more.'"
Merkel also recalled the tragic side of Nov. 9 for Germans – the Nazis' Kristallnacht, or Night of Broken Glass – an anti-Semitic pogrom 71 years ago. At least 91 German Jews were killed, hundreds of synagogues destroyed and thousands of Jewish businesses vandalized and looted in the state-sanctioned riots that night.
"Both show that freedom is not self evident," Merkel said. "Freedom must be fought for. Freedom must be defended time and again."
Uwe Kross, a 65-year-old retiree, fought back tears as he recalled watching the drama unfold two decades ago, hours after a confused announcement that East Germany was lifting travel restrictions.
"That night, you couldn't stop people," Kross said. "They lifted the barrier and everyone poured through. We saw it first on TV, normally it was very quiet up here, but that night we could hear the footsteps of those crossing, tap, tap, tap."
Merkel, who was one of thousands to cross that night, recalled that "before the joy of freedom came, many people suffered."
She lauded Gorbachev, with whom she shared an umbrella amid a crush of hundreds, eager for a glimpse of the man many still consider a hero for his role in pushing reform in the Soviet Union.
"You made this possible – you courageously let things happen, and that was much more than we could expect," she said.
Later, Merkel also thanked Germany's neighbors to the east. She welcomed several leaders who dared to stand up for democracy, including Poland's 1980s pro-democracy leader, Lech Walesa, and Miklos Nemeth, Hungary's last prime minister before communism collapsed. The two men were tapped to push the first domino.
Music from Bon Jovi and Beethoven recalled the joy of the border's opening, which led to German reunification less than a year later and the swift demolition of most of the wall – which snaked for 96 miles around West Berlin, a capitalist enclave deep inside East Germany.
In the decades it stood, 136 people were killed trying to make their way across the border and the wall came to represent the split in ideologies between the communist East and the democratic West.
"This wall divided not only a single country but, as we realize today, all of Europe," Medvedev said, taking his turn in a series of speeches by leaders gathered at Berlin's Brandenburg Gate for the ceremonies.
He said the wall was "destined to fall" amid reforms that were gaining momentum in the Communist Soviet Union and other countries in Eastern Europe, which was dominated by Moscow. "The role of the Soviet Union in that period was truly decisive."
By the Brandenburg Gate, which stood in a no man's land behind the wall for nearly three decades, Dieter Mohnka, 74, and his wife Helga, 71, shared a bowl of French fries on Monday afternoon and recalled the night the wall was opened.
"We were shocked when we heard that announced, simply astounded," Helga Mohnka said. "The next morning we went straight to visit my aunt in the West."
Dieter Mohnka, a high school teacher at the time, said he had long been fascinated with West Germany.
"I was born in East Germany, I went to school in East Germany. I was supposed to teach the kids about the wonderfulness of the East, when I was secretly watching TV from the West," he said.
Associated Press writers Geir Moulson, Mary MacPherson Lane and Laura Stevens contributed to this report.