With its sweeping marble façade, the five-story mansion along East 64th Street, on one of Manhattan’s most prestigious blocks of town houses, softly bespeaks New York’s inimitable style of sophistication. A bronze door unveils a grand entrance hall with a marble floor, fireplace, and elegant circular staircase. A second bronze door leads to a three-room office and opulent massage and exercise rooms. The enormous drawing room dominates the second floor, behind which a firelit library, screening room, and terrace beckon. The third floor holds the formal dining room, wine cellar, handsome stainless-steel kitchen, and bay-windowed breakfast room. Bedrooms on the fourth floor are crowned by a fifth floor devoted entirely to the master suite—where a resplendent private haven with a stately study and two sumptuous marble-and-stone baths bestows quietude for the city that never sleeps.