Mystic Lake is fast approaching the Jan. 1 deadline for its latest expansion, which will transform the Prior Lake entertainment complex into one of the Twin Cities’ largest hotels — just in time for Minneapolis to host Super Bowl LII.

The ambitious $90 million-plus project will attach a nine-story, 180-room hotel and event center to the existing 586-room Mystic Lake Casino Hotel, adding two ballrooms and a massive glass atrium with scenic views of the golf course.

Treasure Island Resort & Casino near Red Wing also plans to open an expansion by the end of the year that will have 21 more rooms than Mystic Lake. The biggest hotel in the state is the 821-room Hilton Minneapolis.

The Shakopee Mdewakanton Sioux Community (SMSC), which owns and operates Mystic Lake and nearby Little Six Casino, said growing demand was the catalyst for the expansion. It’s on track for an early January opening and already is fully booked for the Feb. 4 Super Bowl at U.S. Bank Stadium.

“There is no wiggle room,” said Tom Polusny, Mystic Lake Casino Hotel’s executive VP of operations. “The only thing that would prevent it being done on time is an act of God.”

The addition, dubbed Mystic Lake Center, will include a 70,000-square-foot event center with several breakout meeting rooms and executive spaces to help attract lucrative convention business.

Officials say the sheer size of the expansion will result in a more diverse clientele, opening the door for large-scale events like concerts, weddings and theatrical productions. A huge industrial kitchen behind the ballrooms can serve up to 3,000 people. Previously, Mystic Lake was mostly limited to crowds under 500.

On Thursday, construction crews fitted insulation in interior walls.

Holland Tudor, Mystic Lake’s group sales manager, pointed to design elements intended to reflect Minnesota’s natural landscape: a flowing ceiling pattern meant to represent a riverbed, curved wood paneling for wild grasslands and blue glass chandeliers for water droplets.

“We want it to feel as a resort rather than a convention center,” said Tudor, gesturing to a picturesque view of the Meadows at Mystic Lake golf course and a nearby wind turbine. “It’s something you can’t get downtown and at some of the other properties right now.”

Each of the hotel’s 18 new suites also enjoy that view.

Though there’s still much work to do inside the luxury tower, advance reservations include some as far in the future as 2023. And executives began selling room blocks to the NFL more than a year in advance of kickoff.

It’s not unusual for hotels to book rooms before construction is finished, but the move is not without risk. If the project is delayed for some unforeseen reason, it could mean lots of angry customers — or even a lawsuit, said Kirby Payne, a hotel consultant and president of HVS Hotel Management in Newport, R.I.

“Nobody wants to book a room that might not be available — because there aren’t alternatives, especially at a time like the Super Bowl,” Payne said.

But Mystic Lake managers say they have no doubt that Burnsville-based PCL Construction Services Inc. is up to the task. The can’t-miss deadline was established before the company broke ground in spring 2016.

“This project has been on the fast track since the beginning,” said Polusny. The SMSC has contracted with the company for big renovations since the 1990s, he said, and “they’ve never missed a deadline they said they can make.”

Mystic Lake will also be the site for “Club Nomadic,” a four-day pop-up concert venue for 9,000 entertainment seekers during Super Bowl weekend.

Because the Indian tribe is a sovereign nation, the plan does not require city approval. Tribal government authorized the expansion, which is expected to create 120 new permanent jobs.

A countdown timer on the project’s website informs visitors that only 94 days remain until the center’s grand opening. And it better be, administrators say, because the first corporate event is booked for Jan. 4.

Prior Lake Mayor Kurt Briggs said he hopes Mystic Lake will bring an influx of visitors to town during the biggest sporting event of the year and bolster the local economy.

“We look forward to rolling out the red carpet for them,” Briggs said. “It is a golden opportunity to highlight our community.”