Zac Posen may love taking fashion risks, but when it comes to real estate, it’s all about the classics. The designer and “Project Runway” judge has just poured $3.5 million into an elegant Upper East Side penthouse, LL NYC shares. The duplex spread sits atop an Emory Roth-designed prewar at 210 East 73rd Street and comes steeped in ornate details like hand-painted ceilings, an iron staircase and a Chesney marble mantle. While the current decor is most certainly in need of a modern facelift, Posen will have plenty of space to flex his creative prowess. The penthouse is a classic six with two bedrooms, two and a half baths and a large 1,800-square-foot wrap terrace. And did we mention there are seven custom closets? Four of them are walk-in!