Mortenson Development is in talks with the city of Minneapolis to bring a 30-story luxury apartment building downtown, filling out plans by Opus Development to turn a city block formerly devoted to parking into dense urban real estate.

Minnetonka-based Opus is building a 26-story luxury apartment tower, called Nic on Fifth, which would occupy the southwestern half of the block bounded by South 4th Street and Marquette Avenue. A new headquarters for Xcel Energy, also by Opus, will replace a parking garage at the corner of Nicollet Mall and South 4th Street. 4Marq, as Mortenson’s proposed tower at 400 Marquette Avenue South is called, fits 262 apartments on 30 floors on top of the remaining 14,000 square feet of the property.

Minneapolis-based UrbanWorks Architecture is designing the building. Mortenson spokesman Cameron Snyder said the project seeks to further the goal of the city’s Plan for Sustainable Growth, which mandates strengthening the city’s urban core and encouraging the use of public transportation.

The building’s podium is a private parking structure with space for 217 cars and 262 bicycles. Wrapped in perforated metal panels with three different colors, the podium appears to gain a certain rhythm from the irregular profiles of the metal panels. A white framework of precast panels overlays 7-foot-tall windows, extending upward from a patio space atop the parking podium like an exoskeleton framing the building’s slender mass. Planter boxes will decorate spaces between the precast panels on lower levels. The structure itself is post-tensioned concrete with anodized aluminum.

Meant for downtown residents young and old, according to Snyder, building facilities include an outdoor pet exercise area, a 24-hour concierge, a business center, fitness center, and a pet grooming center. The ground floor is given over to retail. Outdoor space on the 9th and 30th floors will be reserved for tenant use.

The building has been approved by the Downtown Minneapolis Neighborhood Association but awaits approval from the Planning Commission, which is expected in early June. If all goes smoothly, the 4Marq is expected to be completed by the end of 2014.