Chancellor Angela Merkel, President Christian Wulff and others gathered at what was once the Parliament building in the former West German capital, Bonn, for a ceremony marking the anniversary.
West Germany and communist East Germany were united on Oct. 3, 1990, less than 11 months after the east opened the Berlin Wall.
The identity of West Germany, and later of the reunited Germany, "has been closely linked from the beginning with the commitment to Europe," Supreme Court chief justice Andreas Vosskuhle told the country's leaders.
Mr. Vosskuhle said that European institutions "must not immunise themselves against criticism from their citizens," and that "where Europe is going must not be decided in elite circles alone."
"At the same time, we must always make clear that Europe cannot be reduced to a simple mathematical calculation," he said. He added that the EU is based on the recognition that long-term peace and prosperity can only be secured by a close union and "that goes for good as well as bad times."
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