Salvador Rueda, the director of the Urban Ecology Agency, the agency that designed the superblock model, said a lesson learned from earlier superblocks was that initial opposition gave way to acceptance, in part because of a growing consensus about the benefits. No one has sued the city to remove a superblock, Mr. Rueda said. “Now we know that the main problem is the resistance to change that occurs at the beginning of the implementation of the superblocks.”

In Gràcia, where more than two-thirds of the streets were turned into public spaces, car traffic has dropped to 81,514 trips annually from 95,889 before the superblocks were established. Street life is thriving: Pedestrians now make 201,843 trips annually through Gràcia, up 10 percent from before the superblocks. Cyclists make 10,143 trips annually, a 30 percent increase.

The transformation has been even more significant in El Born, which by the 1990s had become so run-down that many people avoided it. “It was very tough to walk because they used to park cars on top of the sidewalk,” recalled Isabel Ruiz, 53, a longtime resident of the neighborhood.

On a recent afternoon, Jaime Batlle and Iñaki Baquero, who teach architecture at the International University of Catalonia, walked along El Born’s cobblestone streets pointing out changes the superblock had produced. Palm trees and benches were in the middle of streets. Trash was collected by an underground pneumatic system rather than trucks.

There were no curbs or sidewalks, only a single lane that Mr. Batlle called a “common platform” for drivers and pedestrians so that no one felt more ownership. The lane also forced drivers, when allowed in the street, to drive cautiously. Where storefronts once stood empty, customers now flowed in and out of restaurants, wine shops, hair salons and boutiques.

“It used to be full of cars, and now it’s not,” Mr. Batlle said. “Imagine that for the rest of the city. This is the kind of city we want everywhere.”