Built in 1873 as a four-story town house in what is now the elite Upper East Side’s Historic Treadwell District, the ravishing stucco ensemble—today with a fifth and partial sixth floor—is a city symphony of sophistication and elegance. A marble entrance stairhall sets the tone, beyond which a paneled library views a trellised garden. Highlights of the second floor are the formal drawing room, its oak floor trimmed in ebony parquet de Versailles, and a dining room with green marble mantel. Two master suites fill respective floors above. The fifth floor offers more bedrooms and a duplexed bedroom with stairs to a sixth-floor sitting area.