distance between ground level and sea level. However, Linden Terrace is not the island's highest natural point, which is located within Bennett Park a few blocks south, above sea level. Linden Terrace is supported with stone retaining walls of up to tall. It comprises a main observation deck and the smaller Northeast Terrace, which are linked by an arch across a passageway below. In the early 21st century the terrace was renamed after John D. Rockefeller Jr's last surviving child David, who had donated $1 million toward the park. The main portion contains a terraced seating area with elms. There is plaque installed in 1935 that recognizes John Rockefeller Jr's donation of the parkland, as well as another plaque installed in 2010 honoring David's donation. The Northeast Terrace, also known as Flagpole Terrace, includes a flagstaff with a granite-and-bronze pedestal. The original flagstaff installed by Olmsted was toppled during Hurricane Sandy in 2012 and was replaced with a replica. The retaining wall north of Linden Terrace contains a stele called the Fort Tryon Memorial. The stele predates the park, having been installed in 1904 or 1909 to a design by Charles Rollinson Lamb. The monument was donated by C. K. G. Billings and the American Scenic and Historic Preservation Society. It contains an inscription commemorating Corbin's and the Maryland and Virginia regiments' defense during the battle on Forest Hill in 1776. Billings estate There are numerous remnants of the C. K. G. Billings estate. The Fort Tryon Cottage, located on a slope just northwest of Corbin Circle, was originally a gatehouse for the estate. The structure is made of frame and stucco and contains three floors with a dining room and kitchen, as well as a patio. The cottage is NYC Parks' northern Manhattan headquarters and is closed to the public except for one weekend per year. Another extant remnant of the estate is the partially paved-over red-brick pathways near Corbin Circle. It was originally a serpentine driveway with multiple switchbacks that continued down to Riverside Drive, now the northbound lanes of the Henry Hudson Parkway. The brick was intended to help horses ascend the driveway's 6% slope. By 1936, when the park was built, the driveway had been converted into a pedestrian path. Though the gates to the driveway were removed, the granite posts were left standing. An overgrown section of the driveway used to connect with the northbound