Modern Makeover for Wrigley Building, Long a Hallmark of Chicago's Skyline CHICAGO - The renovation of the landmark Wrigley Building, one of the beacons along this city's Magnificent Mile, is an effort by an investor-turned-developer to reposition one of Chicago's most famous structures amid the city's expanding retail district. The $70 million project, including $12 million in city tax breaks, is nearly complete, with a commitment from an anchor tenant at street level and leasing efforts for the upper floors underway. The building's developer, BDT Capital Partners, is an investment and financial advisory firm founded in 2009 by Byron Trott, a former vice chairman of investment banking at Goldman Sachs, as well as an adviser to Warren E. Buffett. The firm, which has a $3 billion investment fund, specializes in advising family-controlled businesses, including those associated with the Pritzker, Mars and Wrigley families. For nearly a century, the building, which is on North Michigan Avenue, was associated with the William Wrigley chewing gum company, which created such brands as Juicy Fruit, Spearmint and Doublemint gum. After Mars acquired the company in 2008 and sold the building to Mr. Trott's firm for $33 million, the Wrigley company last year moved out and consolidated its Chicago operations at a research center it owns northwest of downtown. Just north of the Chicago River, the gleaming white twin-tower complex has been under renovation for over a year, with everything above its first floor gutted to turn it into a modern office complex. On the outside, the elaborate Spanish baroque terra cotta facade was repaired and cleaned and about 2,000 windows were replaced. One of the biggest changes, however, involved doubling the amount of retail space in the complex to about 65,000 square feet on the first and second floors and creating an open-air shopping arcade along the city-owned plaza between the two towers. The structure, which will continue to be known as the Wrigley Building, was completed in 1924 and has become a cherished local landmark. "There aren't that many buildings in Chicago where you don't have to use an address when you get into a taxi, but the Wrigley is certainly one of them," said Ari Glass, executive vice president of Zeller Realty. His company is handling the leasing for the newly renovated building. Mr. Trott's other partners on the project include the Groupon co-founders Eric Lefkofsky and Brad Keywell. Mr. Trott's BDT offices look out on the Wrigley's heavily ornamented clock tower. "It's the iconic building of Chicago, and one of our most important clients owned it and trusted us to own it for the next 20 years and treat it as they wanted it to be treated," he said, referring to Mars. The project's added retail space acknowledges how high ground-floor retail rents along Michigan Avenue are, topping out at about $500 a square foot. By contrast, office rents in the area are in the $30 to $40 a square foot range. "The retail rents along Michigan Avenue are enormous, and the Wrigley organization had not taken advantage of that over the years," said Michael Kaufman, managing partner of Goettsch Partners. The arcade was a big financial plus for the project. But the company has discovered, according to Robbie Robinson, managing director of BDT, that despite its prominent location and status, the Wrigley Building remains something of a mystery to many people. The project partners have been reintroducing the building, which still has a 60 percent vacancy rate, to the business community. "For every five brokers we have brought into the building," he said, "at least three have said they've never been in here before." Several new retail tenants have been signed, the most prominent of which is Walgreens, which announced that it leased 28,000 square feet on two levels in the building's north tower for what it calls a "flagship" store.