ISAAC MIZRAHI’S GREENWICH HOME is the definition of understated sophistication. Set in an historic 1931 building just off Sixth Avenue, the American fashion designer’s three-bedroom apartment is the result of an amalgamation of three apartments that took 20 years to create. Mizrahi renovated the original one-bedroom more than two decades ago, then purchased a studio two doors down. When the two-bedroom that separated his apartments finally became available, he made his move and set about to create the calming and light-filled space, filling it with lovely things, such as a 19th-century pedestal table and Danish-modern Ole Wanscher chairs, books and antiques and a 1930’s Steinway piano. There is also a terrace that overlooks the rooftops of the city . . .