BERLIN — Chancellor Angela Merkel thanked former Soviet leader Mikhail Gorbachev for making change possible in East Germany as she visited what was once a fortified border crossing on Monday, retracing her steps from the night the Berlin Wall fell 20 years ago.

The Bornholmer Strasse bridge was the first crossing to open on Nov. 9, 1989, following a confused announcement that East Germany was lifting travel restrictions  — a pivotal moment in the collapse of communism in Europe.

Merkel, who grew up in East Germany and was one of thousands to cross that night, recalled that "before the joy of freedom came, many people suffered."

She lauded Gorbachev, who crossed the bridge alongside her to cheers of "Gorby! Gorby!" from onlookers, for his role in pushing reform in the Soviet Union.

"We always knew that something had to happen there so that more could change here," she said.

"You made this possible — you courageously let things happen, and that was much more than we could expect," she told Gorbachev in front of several hundred people gathered in light drizzle on the bridge over railway lines.

Merkel also welcomed Poland's 1980s pro-democracy leader, Lech Walesa, to the former crossing, saying that his Solidarity movement provided "incredible encouragement" to East Germans.

The leaders were joined by prominent former East Germans such as Joachim Gauck, an ex-pastor who later oversaw the archives of East Germany's secret police, the Stasi.

"Those in government thought they were opening a valve, but once it was open much more happened," Gauck said of the border opening. "A collapse followed."

The bridge crossing was one of a series of events marking Monday's anniversary of the border's opening after the wall kept East German citizens penned in for 28 years

Music from Bon Jovi and Beethoven was to recall the joy of the border's opening, which led to German reunification less than a year later as well as the swift demolition of most of the wall, which snaked for 155 kilometers around West Berlin, a capitalist enclave deep inside East Germany.

Memorials also were planned to the 136 people killed trying to cross the border. Candles were lit and 1,000 towering plastic foam dominoes placed along the wall's route were to be tipped over later Monday.

Also expected in Berlin for the ceremonies were the leaders of all 27 European Union countries and President Dmitry Medvedev.