A 400-room hotel could replace the old Ramsey County jail or the West Publishing building on Kellogg Boulevard.

A movie theater, retail center and towers of offices and housing with above-ground parking could line each side of Wabasha Street.

The Seven Corners, Custom House and Central Station sites would be so adorned with activity, they would be almost unrecognizable.

For a downtown that saw its last department store close last year, a task force of St. Paul business leaders is dreaming big. So big, in fact, they readily admit that not all of their ambitious plans will come together.

The hope is, however, that by sharing concept drawings, they’ll jump-start interest in downtown St. Paul.

At 10:30 a.m. Friday, Mayor Chris Coleman will join two task force co-chairmen, Ecolab CEO Doug Baker and Greater MSP CEO Michael Langley, to unveil the “Prosper: Momentum is Building” report — a series of illustrations and planning scenarios waiting for developers to come by and turn them into reality.

The group has spent the past year meeting with real estate brokers, regional and national developers and St. Paul business owners to explore the “highest, best and most practical uses for the sites,” according to a statement from the mayor’s office.

The four redevelopment sites are Seven Corners Gateway in front of Xcel Energy Center, the Macy’s-Grace Building-Wabasha Court area, the new Central Station light-rail stop on Cedar Street and the Ramsey County Government Center West buildings along the Kellogg Boulevard river bluffs.

The 32-page report notes that downtown already has built a strong foundation for future development. Metro Transit’s 11-mile Central Corridor Light Rail Transit line, or Green Line, will begin rolling June 14. The county has remodeled the Union Depot transit hub, which will welcome Amtrak this year. A 7,000-seat regional ballpark will open by May 2015.

The Lafayette and Cayuga Bridge and highway projects are underway, not far from five major medical facilities that line the outskirts of downtown. Transit studies are analyzing the possibility of adding streetcars to Seventh Street and Bus Rapid Transit on Robert Street, and plans call for a loop of bike lanes at sidewalk level touching the Kellogg Mall and the future Pedro Park.

An old axiom has it that business follows residents, and residential construction has been moving at a rapid pace downtown, sometimes as a result of city interventions. Downtown St. Paul has a population of about 74,000 workers and 8,100 residents, according to the report, and its residential population has grown 28 percent in the past 10 years.

Private developers already have remodeled the three Pioneer-Endicott buildings and are on the verge of converting the old Post Office tower on Kellogg Boulevard into housing and other uses. The city has opened luxury apartments at the Lofts at Farmers’ Market and the Penfield.

Old office and warehouse spaces such as the Renaissance Box in Lowertown and Minnesota Building on Cedar Street have been converted into apartments for low- and moderate-income workers. And across the Mississippi River, the West Side Flats housing development is almost complete.

In short, city officials say they have the right mix and critical mass of people to entice developers to move to the next level of “mixed use” construction: hotels, retail, high-end Class A office space and housing, sometimes in a single complex.

That model has found stronger footing in downtown Minneapolis complexes such as the 32-story Marriott Hotel City Center building and the 36-story Plaza Seven building, which is home to an underground parking garage, a 14-story Radisson Hotel and an office tower.

The mayor’s office hopes it can work downtown St. Paul, as well.

City Center Realty Partners, the San Francisco-based firm that bought Plaza Seven in Minneapolis, had planned to add the vacant Macy’s building to its holdings but negotiations with the department store company fell apart. The St. Paul Port Authority has since purchased the Macy’s site and will determine whether to sell the building or raze it.

When arts offerings at the Ordway Center and sporting events at the Xcel Center are not in session, downtown St. Paul can be quiet.

Nevertheless, events such as the Winter Carnival, Red Bull Crashed Ice, the St. Patrick’s Day parade and the Northern Spark arts festival have been known to draw up to 100,000 people downtown, and city officials see those numbers as proof that interest in living and working downtown remains high.

Frederick Melo can be reached at 651-228-2172. Follow him at twitter.com/FrederickMelo.

DOWNTOWN’S POTENTIAL

SEVEN CORNERS GATEWAY

Fronting Xcel Energy Center, the site links downtown and the West 7th Commercial District. The concept plans call for a 650-room hotel, a 22,000-square-foot ballroom and event space, and 25,000 square feet of retail. A two-story courtyard or meeting space would span an additional 50,000 square feet. Seventh Street could be closed during events to enhance the plaza feel.

GOVERNMENT CENTER WEST

Situated on a 100-foot bluff, the old county jail, the West Publishing building and other properties on the riverfront side of Kellogg Boulevard offer great views but a construction challenge. Plans call for a 400-room hotel, 100,000 square feet of retail and commercial space, and 300 units of housing in a residential tower. Development at the base of the bluff could be lined with parking and an additional 150 units of housing, and create a public path to the river, “capturing the spirit and imagery of a European hill town.”

MACY’S-GRACE-WABASHA COURT

Macy’s, Wabasha Court and the former Grace Building could become an important link to the 7th Place pedestrian mall and the historic Hamm Building block. The concept plan calls for 200,000 square feet of retail and entertainment space in two stories fronting either side of Wabasha Street, an 80-room boutique hotel, 230 condos in a residential tower, and a second tower featuring 400,000 square feet of higher end, or “Class A,” office space.

CENTRAL STATION

The light-rail station will begin service June 14, and the new Central Station stop at Fourth and Cedar streets creates an opportunity for a development with built-in transit access. A public park or plaza would sit at one end, with a building situated over and around the station itself. The plan calls for 192,000 square feet of Class A office space, 16,000 square feet of commercial and retail space, and 250 apartments or condos.