The Ramble and Lake in Central Park together form an inseparable central feature of Frederick Law Olmsted and Calvert Vaux's "Greensward" plan (1857) to provide a Central Park for New York City. The Ramble was intended as a woodland walk through highly varied topography, a "wild garden" away from carriage drives and bridle paths, to be wandered in, or to be viewed as a "natural" landscape from the formal lakefront setting of Bethesda Terrace (illustration below) or from rented rowboats on the Lake. The 38-acre (150,000 m2) Ramble embraces the deep coves of the north shore of the Lake, excavated between bands of bedrock; it offers dense naturalistic planting, rocky outcrops of glacially-scarred Manhattan bedrock, small open glades and an artificial stream, The Gill, that empties through the Azalea Pond, then down a cascade into the Lake. Its ground rises northwards towards Vista Rock, crowned by Belvedere Castle, a lookout and eye-catching folly.