From the top of this hill, the highest point on the property, much of the original Jay estate could be seen. During the early 1900s, the Jays built a grass tennis court here, and the court was later used for croquet. Across the fields south of the main house on another promontory once stood the 1852 home of John Jay’s grandson, John Jay II. In 1925, Eleanor Jay Iselin, the great-great-granddaughter of John Jay, built a children’s playhouse for her son Arthur Iselin, Jr. Today, a reconstructed playhouse contains a small exhibit on the structure’s restoration. There was no garden in the courtyard when the Jays and Iselins lived here. Today, the Hopp Ground Garden Club maintains a garden here for the benefit of those who are unable to enjoy the unpaved gardens located in other areas of the site, and this garden includes plant materials from those other gardens.