City officials Wednesday unveiled an ambitious plan aimed at transforming the Denver Performing Arts Complex from a nighttime cultural destination to an urban hub where people live, work, learn and play 24 hours a day.

The plan, which would involve public and private investment, has no price tag yet, but it is designed to diversify the offerings and audiences at the 12-acre site that houses the city’s biggest theaters. It will also, to the relief of art patrons, add 50 percent more parking.

The project is tied to major improvements that will add an additional floor to the Colorado Convention Center next door.

Among the highlights:

• Tearing down 2,600-seat Boettcher Concert Hall and building a 1,200-seat venue at the corner of 14th and Arapahoe streets, where there is a parking garage. The Colorado Symphony, which has been seeking a smaller home base, would perform there.

• Adding three residential towers to be constructed by private developers. Renderings show the buildings, which could house 1,000 residents, reaching as high as 40 stories.

• Moving high school students from the city’s performing arts magnet program in east Denver to a new building on the spot now occupied by Boettcher.

• Creating an expanded outdoor park in place of the Sculpture Park along Speer Boulevard. The park would include an outdoor pavilion raised three stories off the ground to meet the rest of DPAC (and avoid noise from busy Speer).

• Adding a parking garage under the raised art park, upping the current total of spots from 1,700 to more than 2,600.

• Adding intimate performance venues with a couple hundred seats that could be rented by smaller arts groups that have little use for the current venues, which each seat more than 2,000. There also would be incubator spaces for arts groups.

Ginger White-Brunetti, deputy director of Denver’s Arts & Venues Department, cautioned that the plan is in the conceptual phase as she unveiled it to the City Council’s Infrastructure & Culture Committee on Wednesday. The various elements can be developed as separate parts, and the market will determine the size and scope of such things as the residential towers.

But they are designed to open up the space to greater use, both indoors and out. The arts complex is “a great and vibrant place when all of our houses are going,” she said. But during the day, one of Denver’s prime pieces of real estate “can be a quiet, sleepy place.”

Key to the strategy are new entrances. The current main entrance, at Curtis and 14th streets, would be widened to create a courtyard, giving visitors a set-back view of the Ellie Caulkins Opera House. The plan envisions additional pathways into the complex core from Arapahoe Street and Speer.

Patrons also could arrive at the center on two wheels, via the trails along Cherry Creek, and park at a bicycle station in the new park. White-Brunetti laid out the idea that people could bike in, bring a picnic dinner and catch a performance simulcast from the indoor theaters to the outdoor pavilion, perhaps for free.

Arts & Venues faces a number of hurdles in completing the plan. It depends on, as White-Brunetti put it, “site leveraging” — raising cash from private developers who stand to profit from the residential towers. Their willingness to step up could depend on the health of the region’s economy. Because of the performing arts academy and the park addition, both Denver Public Schools and Parks & Recreation are potential funding partners.

Arts & Venues hopes to begin asking for design proposals in 2017.

The agency already has the money for the convention center addition, which voters approved in November as part of ballot measure 2C, which also paid for improvements on the National Western Stock Show grounds.

The $105 million project will add as much as 85,000 square feet in ballroom and meeting space. There will be technology upgrades and a splashy roof deck.

The center adds $550 million a year in economic benefit to downtown Denver, according to Arts & Venues executive director Kent Rice and is one of the top-rated meeting places in the country. “To keep it that way, you have to stay competitive,” he said.

Ray Mark Rinaldi: 303-954-1540, @rayrinaldi or rrinaldi@denverpost.com