The City of Cambridge and Square businesses are involved in a joint effort to transform Palmer Street, the now-secluded road threaded between the Palmer Street Coop and the Mass. Ave. Coop.

“Instead of a tired alley, [Palmer Street] will become a really terrific corridor,” said John DiGiovanni, a Square real estate maven whose company owns the Garage, and an investor in the Palmer Street project.

Plans call for the addition of video screens to both sides of the Coop’s elevated walkway and columns on both sides of the street.

The City of Cambridge has also committted $3.5 million thus far to the revamping of the Square.

The crosswalk between Out of Town News and Bank of America will double in size, and a landscaped pedestrian island will be built in front of the Lampoon building on Mount Auburn Street, among other improvements.

“It’s fair to say that [the Harvard Square project] will be the biggest revitalization [in] a couple of decades, even a quarter century,” DiGiovanni said.

Turnover continues among the Square’s restaurants, with Brother Jimmy’s on Winthrop Street closing in May, and plans for two new eateries—Hoffa’s Swiss Alps and Phatt Boys, a “Southern barbecue seafood shack”—in the works.

And Cafe Pamplona, a Bow Street restaurant open since 1959, closed its doors last December when its 88-year-old owner, Josefina Yanguas, announced she was retiring.

But the cafe was up and running again by May, after Yanguas rejected several offers to buy or lease the cafe.

—Staff writer Brendan R. Linn can be reached at blinn@fas.harvard.edu.