When Edward Durell Stone renovated this Upper East Side townhouse in 1956, he drew inspiration from Frank Lloyd Wright for its signature element, the façade. Stone, who made the New York City building his home, replaced its existing forward face with floor-to-ceiling windows, then covered it with a decorative concrete grille. Although the building was landmarked in 1981, the renovation was controversial for its time and would be all but impossible under current laws. The house, which is listed for sale by Sotheby’s at $9.995 million, is unique—and unalterable. Its previous owner, Knoll CEO Andrew Cogan and his wife, Lori Finkel, secured an easement to guarantee that the street façade, whose pattern is echoed throughout the nearly 5,000-square-foot house, could never be changed.