Blackbird Investments plans a 29-story mixed-use building in a vacant site once occupied by Younkers department store in downtown Des Moines.

The building would include 220 residential units that would include market-rate rental apartments and for-sale units. In addition, it would have 7,000 square feet of ground-floor retail fronting Walnut, a spokesman for the investment and development group said.

The firm also is considering a 150-room full-service hotel in the building and is negotiating with possible flags.

Blackbird currently is renovating what is now called the Wilkins Building on the west side of the Younkers lot.

At 29 stories, the structure would be the second-tallest residential tower in Des Moines. Mandelbaum Properties has proposed a 32-story mixed-use building at the site of the parking ramp at Fifth Avenue between Court Avenue and Walnut Street. The Plaza Building has 25 stories.

The Blackbird Investments project would include two floors of penthouse suites.

Approximately 75 percent of the exterior would be clad in glass.

At the Wilkins Building, the original structure at the former Younkers site, Blackbird has started work on a $20 million project that includes 10,000 square feet of ground-floor commercial space, restoration of the Younkers Tea Room space for banquet and other assembly use, and 60 residential apartments.