It happened over the noon hour last Tuesday as Minneapolis Mayor R.T. Rybak was leading a gaggle of media types on a lively tour of Nicollet Mall, the mayor pausing to point out crumbling pavement and defective streetlights and describing his plans for updating the aging avenue (“It’s totally falling apart”) while trading back slaps and “attaboys” with passersby and, in the midst of all that, putting forward something truly radical:

The next Nicollet will once again be Minnesota’s main street, a bustling place where “everybody belongs,” where “the richest and poorest and everyone in between” will feel comfortable rubbing elbows and sharing a common experience.

The mayor said this with a straight face, as if he thought it unremarkable. But, in fact, such a street would be a radical reversal of history.

For 50 years, Americans have been retreating from public spaces. The private car, the subdivision without sidewalks or front porches, the privatized shopping malls and office parks, the niche TV channels and customized Internet sites — all are part of an increasingly segmented marketplace of styles and tastes that make the mass market and the truly public space almost unknown. Add to that the growing gap between rich and poor and the perception (false) that the world beyond our doorstep is an ever more dangerous place, and you begin to grasp the audacity of Rybak’s idea. Even the State Fair, probably Minnesota’s most egalitarian conclave, happens in a private space with gatekeepers and tickets required for admission.

“We don’t lock people out,” Rybak said, referring to his vision of a remodeled Nicollet Mall. Even now, in its current state of disrepair, for an hour or two at midday in fine weather, Nicollet is probably Minnesota’s best example of a valid public place. Starch-collared corporate types stroll shoulder to shoulder with welfare mothers and their screaming babies. The homeless and mentally ill share benches with office workers trying to catch a little sun. It’s not always a pleasant mix of cultures and manners, but there’s an authenticity to it — and even, perhaps, a sense that we’re still all in this together.

Rybak heaped praise on Target, U.S. Bank and Xcel Energy for keeping and expanding their corporate headquarters on Nicollet and reaping the wider perspectives that public spaces can offer. And the mayor, pointing out the hundreds of new apartments and a new grocery store rising nearby, was right to suggest that Nicollet seems poised for rebirth.

Indeed, a panel of judges will select a design team this week to begin forging the next version of Nicollet Mall. The winner will carry an extraordinary burden. Normally, a marketing study determining demographic and economic trends, a target audience, the appetite for retail, possible changes with transit and so on would precede the design phase. But Minneapolis has taken a “Field of Dreams” approach: Build something spectacular, and they will come. The winning team will be expected to design a public street so compelling that everyone will want to be on it — high life, low life and everyone in between — a place where, in Rybak’s words, everyone belongs. Nicollet would reemerge as a general destination and a signature for the city and state, as it was 40 years ago when Mary Tyler Moore threw her hat in the air.

That’s a very tall order, but a younger generation seems more enthusiastic about embracing the authenticity and the mix of human experiences that well-designed public spaces can offer. Rybak’s dream of a “Nicollet for all” isn’t impossible. New York’s Bryant Park and Chicago’s Millennium Park show that it can be done.

For Nicollet, it’s anticipated that the winning design will include these elements: a greener streetscape thick with trees and other plantings; space for modern streetcars; vertical connections between sidewalks and skyways, and steam heat just below to enhance the mall’s wintertime appeal. While private storefronts won’t be included in the project, the new street would be expected to inspire creativity from retailers, including new storefronts that are transparent to the street and flexible retail spaces that are smaller and edgier than those found in the suburbs.

As always, money is the main concern. The price tag is modest — $40 million. But how the costs are divided among state, city and private sources could cause friction before the new street’s projected opening in 2016.

This would be Nicollet Mall’s third iteration. Lawrence Halprin’s graceful original opened in 1967 as the nation’s first pedestrian/transit mall. A prosaic redesign in the 1980s couldn’t forestall a retail retreat that left Nicollet far behind the Mall of America as a shopping destination. The next Nicollet aims to be the centerpiece of an ongoing transition that recasts downtown as a more appealing and transit-friendly, 24-hour district with housing, parks, offices, culture, entertainment and, yes, even shopping.