A prime parcel off Nicollet Mall has attracted proposals from four developers with transformative visions that include an 80-story tower that would loom over the rest of Minneapolis skyline.

Three established Twin Cities players — United Properties, Mortenson and Doran Development — offered ideas for the site, currently a parking lot across from the Minneapolis Central Library.

But perhaps the most ambitious proposal came from a relative newcomer, Alex Duval, who says the team behind his mega-tower already includes a structural engineer who worked on the world's tallest building, in Dubai.

"We have some extraordinary proposals that are emblematic of what I have called the sexiest block in the city," said Jacob Frey, a City Council member who represents part of downtown. "I think everyone is very pleased."

The city owns the site, commonly called the Nicollet Hotel Block for the building that stood there until 1991. It had sought proposals that would include an iconic building and public park space that would connect the commercial activity of Nicollet Mall, the creative energy of the North Loop and the active outdoors site of the Mississippi riverfront.

The city has high hopes for the plot situated between 3rd Street, Washington Av., Hennepin Av. and Nicollet. Among the list of requirements, proposals had to include some mix of office, hotel, residential and ground-level retail, and allow streetcar access around or through the property.

Duval is bucking the recent trend toward lower-profile buildings downtown by proposing a 900-foot glassy tower that would include a hotel, apartments and office space. The 80-story building would rise about 100 feet and 23 floors above Minnesota's tallest building, the IDS Center.

A smaller eight-story "podium" beside it would contain ground-floor television and broadcast studios, and a green public plaza would serve as a throughway from Nicollet Mall to Cancer Survivors Park. The two buildings would be connected by a glass atrium with a retractable feature for warm days.

Duval most recently worked in development in Miami before establishing Duval Development in the Twin Cities. He's married to Kjersti Monson, the city's director of long-range planning.

Monson has removed herself from the process and filed conflict-of-interest forms.

Duval has assembled a large team of architects, engineers and lawyers. Most notable is Thornton Tomasetti, a structural engineer on the podium to Dubai's Burj Khalifa, the world's tallest building. Duval declined to provide the name of his investors and hotel operator.

While the project would add a dramatic fixture to the Minneapolis skyline, local real estate experts question whether it could be financed.

"Eighty stories? That's a pretty ambitious project. I think you would need a couple of major tenants to get the financing on something like that," said Herb Tousley, head of the real estate program at the University of St. Thomas. "It would be cool to pull it off, but I think they've got a lot of work to do unless they've got someone in their pocket ."

Minneapolis-based Doran is proposing a 30-story residential building and a six-story Graves hotel with a skyway connection between the two. The team includes architectural firm BKV Group and IREIT, a global real estate investment firm.

Founder and principal Kelly Doran said the turnaround time was tight on the proposal, but the quality of his team gives him confidence.

"It was exciting to work on, and this is just the first step of many," he said. "The future trolley would run through the middle, creating a really great space at the street level."

The plan from United Properties, owned by the Pohlad family, includes a 36-story building with a Hilton hotel and 300 residential units. The plan includes street-level retail and restaurants, skyway-level office space and possibly a charter school. Bloomington-based United's green space suggests year-round activities, a grand staircase between the buildings and a cascading fountain to tie in with the nearby river.

Joining United on the proposal are Stuart Development Corp., Aimbridge Hospitality LLC, FRM Associates and LHB architects.

Mortenson senior vice president Ken Sorensen said his team is excited about the project, but wanted city approval before releasing details of its proposal.

The Gateway District has undergone a development boom over the past two years, and these proposals are being considered as downtown Minneapolis prepares for an overhaul of Nicollet Mall, its signature street.

"We worked hard with the city to ask that these proposals include a strong public realm component," said Steve Cramer, president and CEO of the Minneapolis Downtown Council, which is helping spearhead the mall redesign. "We hope that the one that is chosen does that the best."

City staffers will review the four plans and conduct community outreach with the Downtown Minneapolis Neighborhood Association. The City Council is expected to select one of the developers by April and sell the property by late summer 2015. Construction would begin early- to mid-2016.

Staff writer Eric Roper contributed to this report.

Kristen Leigh Painter• 612-673-4767