As the name suggests, large areas of the park are hills, mostly wooded. The park also contains three children's playgrounds; baseball and soccer fields; tennis and basketball courts. All of these facilities are popular with people from the neighborhood, for both organized leagues (including the local Little League) and more casual games. The Urban Ecology Center at the north end of the park is both a location for educational programs and the local headquarters of the park rangers.
The area of the park along the Harlem River includes a small salt marsh that attracts large numbers of waterbirds. Mallards, Canada Geese, and Herring Gulls are year-round residents, using both the water and the nearby lawns and ballfields. Many wading birds and waterfowl pass through on the Spring and Fall migrations, and herons and cormorants often spend the summer.
The woods also support a wide variety of birds, including common species such as Blue Jays and Cardinalss. Birds of prey that breed in the park include Red-tailed Hawks and owls. A project begun in Summer 2002 is attempting to reintroduce the Bald Eagle to Manhattan using nesting boxes in the park. In the first summer, three of the four introduced eaglets fledged successfully.
The park is narrow and surrounded by a major urban area, and the Henry Hudson Parkway and Amtrak railroad tracks run through it. Thus, while it is a welcome oasis in the city, it does not support large wild mammals, and visitors may find it impossible to completely escape the noise of cars.