Yellowstone Park is built on a sloping hillside amidst the apartment buildings of Forest Hills. At the base of the hill is the playground and larger recreational areas, while more passive spaces rise above. The design of the park uses curving ramps and retaining walls throughout to break up the steep slope into more informal areas. According to Ann Butter, who worked on the park, one lawn area was designed around a singular existing tree, now gone. However many of the existing plantings such as birch and hemlock trees still remain an integral part of the park, In addition, Ms. Butter noted the involvement of prominent landscape architect Clara Coffey in the design of Yellowstone Park.