BIG BERTHA: In one of its iterations, as this artist’s rendering shows, Technopolis would have dominated the city’s skyline.

It was a grand vision. Maybe even a noble one. “TECHNOPOLIS.”

A 30-story, 400-foot, steel and glass “gossamer tower” that would rise high above South Station, anchoring what the Boston Redevelopment Authority (BRA) dubbed “a new Southern Gateway to Boston.”

It would house a mighty, world-class, scientific-investigative research engine designed to tackle today’s disease scourges and seek viable pharma treatments and cures for the likes of AIDS, SARS, cancer, the common cold. Also known as the Tufts International Research Center (TIRC), it was intended to be the pre-eminent scientific jewel gracing the city skyline. Its estimated cost: $600 to $700 million.

Technopolis was the shared dream of former Tufts University president John Mayer and former BRA director Stephen Coyle. Mayer believed that Tufts, a small university by Boston’s standards, could find financing and tenants for the new research tower. Coyle, meanwhile, wanted to enhance the South Station transportation hub. “We want to take the biotechnology part of Boston’s economy beyond the medical research now building in the Longwood Avenue area,” he said when the project launched in 1990.

Sixteen years later, however, the air space above South Station is filled only with cloud castles in the sky.

Since the complex’s inception, its architectural plans have shifted course at least three times. At one point, TIRC was redesigned as the tallest tower in the city, eclipsing even the John Hancock Building by a few feet. Then it was scaled down to become the tallest building in the financial district. Last month, even those bragging-rights were lost when local business-whiz Steve Belkin announced the construction of a huge, new skyscraper on Federal Street, smack in the middle of the financial district.

And it isn’t just Technopolis’s physical structure that has been altered. Its mission has changed dramatically, too. No longer bearing the name of Tufts, the project has morphed — now nameless — from a research center into a diluted “multi-use” space consisting of low- and moderate-income housing, commercial office space, retail and dining establishments, and hotel rooms — something like a Southie version of Copley Square.

That is, of course, if it is ever built.

Meanwhile, more than $20 million in public and private funds have been poured into the project.

This is an atypical story, one about a big development project that went awry. A key sponsor died. The university that was supposed to anchor it failed to attract the necessary medical-research partners to make it a go. And the building itself faced opposition from community groups and a federal transportation agency, thanks to its enormous scale.

There are no heroes or villains here, really, although there might have been some liberty-taking with taxpayers’ money. Rather, this tale concerns a grand vision that gradually slid into the mundane.

LOFTY AMBITIONS: In 1990, the Tufts University International Research Center was planned as a medical-research complex 400 feet tall. By 2000, plans called for creating the tallest building in the Hub.

At the outset, in 1990, Technopolis/Tufts International Research Center was intended to create a city within the city. Consisting of 500,000 square feet of research space, a 675-room Hilton hotel/conference center, 26,000 square feet of retail space, 12,000 square feet of child-care facilities, a health club, and a 1200-car garage, the finished development — most of which would be constructed turtle-back-style over the rail lines — would amount to a massive 2.4 million square feet of space.

Tufts was to anchor the development with 100,000 square feet of university, grant-related research programs. Offices of the federal Food and Drug Administration and the National Institutes of Health would also be located there, along with incubating, start-up, biotech ventures.

Spearheading the ambitious project was the inspirational force of John Mayer. Flamboyant, French-born, and an internationally renowned nutritionist, Mayer was the recipient of 14 World War II decorations from his homeland, including the rank of chevalier in the Legion of Honor. While president of Tufts, he acted as a true visionary. He established the only veterinary school in New England and the region’s first graduate school of nutrition, raised the university endowment from $30 million to $200 million, and brought to the Boston medical campus the Human Nutrition Research Center tower, funded by the US Department of Agriculture.

He was a university-builder, no question about it. Mayer “wasn’t afraid to do things the way he wanted, no matter what,” said Dr. Kenneth Katin, director of the Tufts Center for the Study of Drug Development.

Obsessed with the project, and tirelessly pushing it — even in the face of resistance by university faculty and staff who believed it was too much for Tufts to handle — Mayer left the presidency in 1992 to devote himself full-time to Technopolis.