Late last month, the $51 million duplex penthouse at Trump Park Avenue quietly came off the market, a year after the Elliman broker Victoria Shtainer listed the 6,200-square-foot sprawl, and seven years since Mr. Trump bought the building. "We haven't sold it," Ms. Shtainer said this week. "The timing was not good, so I didn't get any offers."
That's the story with New York's most outstandingly lush real estate. Of the 10 properties that...
