Fifth Avenue’s prime Midtown shopping stretch between East 40th and East 61st streets is the city’s no. 1 generator of office and retail property taxes compared to any similar set of blocks — a whopping $1.53 billion every year, according to the Fifth Avenue Association business-improvement district.

There’s lots of bricks-and-mortar energy on the avenue, too. Rolex is poised to open its glam new tower at East 52nd Street with a flagship store at its base and LVMH is planning a 25-story tower with its own luxury emporium at East 57th Street.

Some major global brands have so much faith in Fifth, they’re buying their stores’ buildings — such as Prada’s $835 million 2023 purchase of 720 and 724 Fifth.

But a threat of uncertainty is barrelling down. The city will soon finalize plans for a $402 million “Future of Fifth” sidewalk and street redesign that will reduce auto traffic to a single lane and create sitting space — but not plazas — for shoppers and sightseers.

The reconfiguration was devised by the city’s Economic Development Corporation under former Mayor Eric Adams but is subject to review by incumbent Mayor Zohran Mamdani’s EDC and the car-hating Department of Transportation. Work is supposed to start in 2027.

“We were behind the plan. We compromised with the city” over certain points, said Madelyn Wils, CEO of the Fifth Avenue Association BID.

“We’ll see whether it holds in the new administration.”

Although the plan currently doesn’t include a bike lane, multiple sources said the pro-bike lobbying group Transportation Alternatives is “pushing like crazy for a bike lane” — which most Fifth Avenue merchants oppose.

The BID wasn’t thrilled about the additional bus lane, partly because, Wils said, “Many of the express buses on the avenue are less than 10% occupied.”

However, she enthusiastically endorsed the sidewalk widening and landscaping because “retailers recognize that if pedestrians have a better experience, there will be more of them.”

A large question mark involves the impact of major underground utilities projects that need to be completed before sidewalks are enlarged.

“Lots of old infrastructure needs to be replaced,” Wils said. 

She hopes the various water main, sewer and electrical jobs can be done in a coordinated way.

“It’s going to be painful, but a lot less painful if we all work together,” she said.

Merchants in Lower Manhattan, for example, were devastated by a Wall Street Area Water Main Project that dug up streets for 10 years starting in the mid-1990s and made parts of Fulton, Wall Street and other streets near-impassable.

But City Hall has yet to put out a timetable or other specifics for the Fifth Avenue utilities project.

Meanwhile, some large, highly visible Fifth Avenue storefronts have stood empty for some time.

Among them: the former Dior space at the GM Building, part of the former Henri Bendel site at 712 Fifth Ave. and 673 Fifth. The latter site is owned by a Chinese company that has kept the space empty for more than a decade.

“I expect 2026 will finish out with a number of very large deals announced and under construction,” said Cushman & Wakefield’s Steven Soutendijk, the broker for several of the available spaces.

The amount of tenant interest “exceeds anything we’ve seen since before Covid,” he added.

CBRE’s Andrew Goldberg shared his optimism, citing the recent arrival of California-based sportswear brand Edikted at landmarked 595 Fifth Ave. as evidence of the avenue’s growing appeal to younger consumers .

Edikted is part of the trend that has seen less expensive fashion brands such as Skims and Mango joining luxury ones like Cartier and Prada.

“If you have a teenage daughter, you know l about Edikted,” Goldberg chuckled.

The influx of retailers with a younger clientele has resulted in some odd juxtapositions.

Swarovski, maker of high-end jewelry and crystal, will now have Chinese-owned Pop Mart as its next-door neighbor. The maker of insanely popular Labubu dolls recently signed a lease for 7,000 square feet at 680 Fifth Ave., where Soutendijk represented the landlord, as The Post first reported.