The absence of the wall is today a handy metaphor for a world whose divisions, religious and cultural, are everywhere and often invisible. At the same time, the wall’s destruction created a new range of urban possibilities. It left vast empty spaces that have turned out to be civic boons in ways politicians and planners 25 years ago did not foresee, just as it freed citizens from the constraints of oppression to explore ambition and opportunity.

The emptiness attracted a new generation. It provided space to dream up clubs in bunkers, galleries in old department stores. Berlin was unfinished, like this generation, which pioneered ad hoc, improvisatory, piecemeal development.

For some of the same reasons that big corporations fled the city — inept government, lack of infrastructure, Detroit-size debts and “the fact that there still isn’t a Whole Foods where you can choose six different types of bananas,” as Mr. Schaefer half-jokingly put it — Berlin suited a post-wall, urban-minded, D.I.Y. generation.

In 1989, Margaret Thatcher of Britain and François Mitterrand of France fretted about whether a single Germany would fall back on old habits. They pictured Panzers rolling down the Champs-Élysées. American news media brooded about a Fourth Reich while recording Berliners’ euphoria when the wall came down. The triumphal narrative came later.

For a long while, the story of reunification entailed unrest, unemployment, division. Many West Germans resisted the economic burden of reunification; East German dissidents had wanted to liberalize East Germany, to gain access through the wall, but not to be annexed.

As with Berlin, so it was with all of Germany that an identity envisioned 25 years ago did not quite come to pass. Today Germany straddles the diplomatic fence between an increasingly assertive Russia and the West. It is reluctant to save Europe from fiscal malaise. Struggling neighbors regard it as a kind of polite bully.