This cooperative apartment house is known for its penthouse that was owned for many years by Conde Nast, the publisher, and its amusing decorative frieze of tortoises and hares.

The penthouse was not the first in the city. Top floors were often allocated previously for servants' quarters, and sometimes for laundry equipment. "Although steam dryers had been introduced early in the century, many people preferred to dry their wash in the sun; tenants in some buildings were allotted specific days of the week when they could have their maids use the rooftop laundry (if it rained, tough luck)," observed James Trager in his book, "Park Avenue, Street of Dreams," Atheneum, 1990.

The penthouse in this building, however, was the first to be widely popularized. "It was certainly the most famous in its day, and remains a benchmark for architectural historians," noted Christopher Gray in a November 7, 1993, article on a cleaning of the building's facade in The New York Times. "Nast inaugurated his apartment, decorated by Elsie de Wolfe, with a housewarming dance on Jan. 18, 1925. His wide-ranging guest list included George Gershwin, Edna St. Vincent Millay, Rube Goldberg, Katherine Cornell, Jascha Heifetz, Fannie Hurst, Fred Astaire, Edward Steichen and John Drew," Gray recounted. The next year, he continued, Nast hired the building's architects, Delano & Aldrich "to design a greenhouse-like glass canopy to cover the terrace and had the ballroom extended to the edge of the building."

The building's three-story limestone base is topped by the tortoise-and-hare frieze that has been adopted by the American Association for the Advancement and Appreciation of Animals in Art & Architecture, founded by Parks Commissioner Henry Stern, as its logo. Just beneath the penthouse is a floor with rounded windows. The handsome but demure building, designed in a Georgian-style with some hints of Art Deco, was developed by Joseph L. M. Mayer.