CLEVELAND, Ohio -- A residential tower at the nuCLEus project in downtown Cleveland could stand 54 stories -- or 647 feet -- high, making it the city's fourth-tallest building.

The developers behind the skyline-changing nuCLEus proposal filed their first crop of renderings with the city Thursday. The images show how Stark Enterprises of Cleveland and J-Dek Investments Ltd. of Solon hope to fit apartments, offices, stores, restaurants, hotel rooms, parking garages and -- possibly -- a few dozen condominiums onto a 3-acre site in the Gateway District.

J-Dek and Stark also confirmed that they've hired NBBJ as the lead architect on the project, which now carries an estimated price tag of $380 million to $400 million. Bialosky + Partners Architects, a local firm, will assist NBBJ designers from Columbus, New York and Shanghai.

"This is an exciting stage in our development process," Bob Stark, president and chief executive officer of Stark Enterprises, said in a written statement. "NBBJ's international reputation and experience will help us create something that is truly iconic for Cleveland."

The project is the second high-rise residential plan to crop up in Cleveland during the last year. Out in University Circle, two local developers are talking about an apartment tower at Euclid Avenue and Stearns Road, on the current site of the Children's Museum of Cleveland.

Downtowns across the country are seeing a surge in high-rise apartment projects, thanks to steady demand for urban living and climbing rents. Cleveland's rental boom, though, is being driven by conversions of older office buildings, many of which qualify for historic-preservation tax credits.

New construction is costly and challenging. Rents here are creeping up, but they're nowhere near what landlords charge in busier, pricier cities. The average rent for a one-bedroom apartment in the central business district is $800 to $1,000 a month, according to the Downtown Cleveland Alliance, which represents property owners.

"We believe downtown Cleveland is in the middle of a renaissance and will need buildings of this height to meet future demands," lead designer A.J. Montero, a partner at NBBJ, wrote in an email Thursday.

The nuCLEus high-rise would be much taller than what First Interstate Properties and Petros Development Corp. are contemplating in University Circle. The initial designs -- which could change as the project evolves -- show that the downtown building could house much more than apartments, though.

At the southeast corner of East Fourth Street and Prospect Avenue, the building would include street-level retail wrapped around a parking garage. Apartments would line the Prospect side of the garage.

Partway up the tower, a six-story bridge would break up the column of residences. That bridge actually is a hotel, which would link the apartment building to an office building to the east. Above the hotel, the tower would hold more apartments and, at the top, potential condominiums.

"We wanted to create a design that would be a contemporary landmark, and yet drew parallels to Cleveland's rich history," Montero wrote in a response to emailed questions. "The design of the bridge in nuCLEus parallels the iconic bridges that cross the river, while at the same time creates a building that people all across the country and even the world will recognize as 'only in Cleveland.'"

Montero and Ryan Newman, who are based in Columbus, are working on the project with New York architect Tim Johnson and Shanghai architect Daniel Ayars, both of whom are well-versed in design and construction of tall buildings.

The entire nuCLEus project could include 500 residences, 1,600 parking spaces, 200,000 square feet of offices and 140,000 square feet of retail, plus the hotel. Stark has waxed poetic about the opportunity to create "laneways" -- alleys lined with small shops, bars and outdoor dining -- as intimate spaces between the development's tall buildings.

J-Dek and Stark plan to seek schematic design approval for nuCLEus from the Cleveland City Planning Commission next week. The project is slated for discussion at a city design review committee Jan. 15, before the commission's Jan. 16 meeting. The project clearly will require zoning modifications and other public approvals.

Ezra Stark, chief operating officer for Stark Enterprises, wouldn't identify specific tenants or discuss potential apartment rents or condo prices. He said the developers still are pulling together their financing from a mix of public and private sources.

Cuyahoga County has committed $3 million in casino-tax revenues, in the form of a loan, to the first phase of the project. Cleveland has put tax-increment financing, which allocates some new property-tax revenues to repaying project debt, on the table. Residential projects in the city also qualify for property-tax abatement.

Stark and J-Dek bought the nuCLEus site in September, as part of a $26 million downtown portfolio deal with a California parking-lot operator. The developers hope to start demolition of a dilapidated Huron Road parking garage and a small Prospect retail building within a few months. Most of the development site is a large parking lot that sits just north of Quicken Loans Area.

Ezra Stark said the developers still hope to open a parking garage before the Republican National Convention, set to take place downtown in mid-2016.

"We're still aggressively pursuing providing some amount of structured parking by the RNC," he said. "We'll provide as much as we can."