Under chilly blue skies Wednesday morning, a ceremonial steel beam was hoisted atop Nic on Fifth, a $100 million luxury apartment tower under construction at 5th Street and Nicollet Mall.

Developed by Minnetonka-based Opus Group, leasing for the 253 units in the 26-story building will begin in January, with completion set for the summer of 2014.

The symbolic “topping-out” ceremony, featuring the steel beam signed by construction workers and Opus employees, typically signifies the halfway point in a big construction project, said Leith Dumas, senior project manager for Opus Design Build LLC. (The beam also features an evergreen tree, said to bring good luck.)

Opus says Nic on Fifth is the first luxury high-rise apartment building in downtown Minneapolis in nearly three decades and the first designed to achieve the coveted LEED environmental certification in the market.

The tower will no doubt help to transform the northern stretch of Nicollet Mall, which has languished for many years. Once Opus completes the tower, it will concentrate on building an expansion of Xcel Energy’s headquarters adjacent to the Nic on Fifth tower.

Meanwhile, Mortenson Development plans to build a 30-story, 262-unit apartment tower called 4Marq at the corner of 4th Street and Marquette Avenue S. to complete the block. Mortenson spokesman Cameron Snyder said the company just notified the Minnesota Pollution Control Agency that it plans to begin work in December.

Kitty-corner from Nic on Fifth, at 5th Street and Marquette Avenue S., the first residents moved into the Soo Line Building City Apartments last month. The renovated 98-year-old building is now 55 percent leased.

The building has a three-story boutique hotel-style lobby, with a floating glass staircase and terrazzo flooring, a private resident lobby and 24/7 concierge service. Other amenities include an indoor/outdoor rooftop pool, a “Sky Club” with a kitchen, fireplace and lounge seating, as well as an outdoor “Sky Park” with sun deck, yoga space, fire pit, bar and grilling stations. A fitness center, business center and conference facilities overlook the lobby.

The developer, Michigan-based Village Green, has opened a leasing office on the skyway level of the building. Rental rates for studios to the three-bedroom, two-bath units range from $1,080 to $4,150. One- and two-bedroom units are available, as well. (Rental rates for Nic on Fifth and 4Marq units have not yet been set.)

The famous Soo Line Building clock, which anchors the exterior corner of 5th Street and Marquette Avenue S., now keeps correct time and lights up with a changing LED face.

Earlier this year, it was announced that St. Paul restaurateurs Russell and Destra Klein, who own Meritage, plan to open Brasserie Zentral in the Soo Line building next spring. The Kleins will also own and operate a wine bar and specialty market called Foreign Legion as well as a skyway-level cafe featuring “European street food” in the second quarter of 2014.

Village Green claims the Soo Line project “broke ground in October 2012 as the first ‘urban core’ housing community in Minneapolis in the last quarter-century.”

Village Green has not publicly disclosed how much the renovation cost.

Stefanie Balsis, Village Green’s regional marketing director, said in a statement that leasing progress “has exceeded our expectations at every turn.”