BERLIN — Frank Ebert, a human-rights activist from East Berlin, was so sure the breach in the Berlin Wall was temporary that he spent part of his first day in the West stocking up on ink, paper, books and other materials that would be impossible to get once he returned to the Communist side.

Within two or three days, though, reality hit. “You couldn’t close the wall again,” recalled Mr. Ebert, who helped to organize celebrations here this weekend for the anniversary of the wall’s demise. “Very quickly it was normal.”

Twenty-five years later, it is so normal that many residents of this increasingly cosmopolitan European capital can hardly relate to life in the heavily militarized, divided city of the days before Nov. 9, 1989. Moritz van Dülmen, director of Kulturprojekte Berlin, the organizer of the anniversary event, estimates that roughly half of today’s residents never had direct experiences with the 96-mile barrier.

Now, slick, modern buildings trace the wall’s footprint. A section of what was known as “death strip” — a sliver of heavily mined land lined by watch towers — is now a park known for its Sunday flea market and open-air karaoke.