For decades, planners and dreamers fantasized over a remarkable expanse of underdeveloped land smack in the middle of the metropolitan area. Covering nearly a square mile, the shaggy patch of industrial property lies mostly north of University Avenue between TCF Bank Stadium and Hwy. 280. It touches Minneapolis and St. Paul as well as the eastern edge of the University of Minnesota’s main campus.

Ambitions for the area focused mainly on commercializing university research as a way to boost the Twin Cities’ technology profile while drawing jobs and investment. Successful research parks adjacent to such universities as Stanford, Duke and North Carolina were often cited as models.

Not much happened. But now, with the light-rail Green Line in place, the real estate market seems suddenly interested in the area’s potential. In recent weeks, the Minneapolis and St. Paul City Councils have approved conceptual plans for a University Avenue Innovation District covering 370 acres. The idea is to build “a city within a city” that would attract an extraordinary fusion of ideas, business, talent and vitality.

There would be no master developer. But the cities and the university would allow the district to establish its own innovative systems for shared parking, heating and cooling, stormwater management, and streetscapes, all meant to raise the district’s efficiency and give it a distinctive green identity.

The potential is impressive: 10,000 jobs, 1,300 housing units and $340 million in additional property tax revenue over the next 10 years, according to Sarah Harris, chair of Prospect North Partnership, the 23-member consortium of public, private and nonprofit members driving the project. Aside from both cities and the university, partners include Greater MSP, the Metropolitan Council, Hennepin County, United Properties, the McKnight Foundation, Xcel Energy and the Trust for Public Land.

“We have one chance to get this right, or we’ll be regretting it for the next 30 years,” Harris said.

Timing is important, because development has already begun. Student housing has exploded around the Stadium Village light-rail station. The U is moving ahead with its east-campus expansion, adding buildings for athletics and a sizable biomedical discovery complex. Several hundred housing units are poised to rise within the Innovation District itself, along with two hotels, a supermarket and a business incubator, all clustered near the Prospect Park light-rail station. The Surly Brewing Co., a popular craft beer destination, opened last year.

What’s most needed now is a greater sense of urgency from the cities, especially Minneapolis, which controls 90 percent of the district. Infrastructure in the area is primitive. Momentum may be lost if new streets aren’t built and old ones repaired, and if city regulations aren’t realigned to accommodate the district’s eco-friendly ambitions.

One innovative idea slated for construction next year is the first phase of a five-block transformation of 4th Street SE. into a strand of plazas, rain gardens and markets, suitable for walking, biking and slow driving — like the Dutch concept woonerf. The stylish street would serve as a demonstration for how the rest of the district might develop. After years of dormancy, a new district with huge potential seems finally ready to arise.