The National Park Service oversees most of the green space in and near the District. Properties range in size from the 184.5-mile-long Chesapeake & Ohio Canal park to tiny triangles of land on Capitol Hill; they vary in character from typical urban park spaces to the National Mall and a marsh. Also included in the park service inventory are memorials, monuments, trails -- and the White House. Park Service properties include:

Anacostia Park, whose 1,200 acres include Kenilworth Park and Aquatic Gardens and Kenilworth Marsh, as well as a golf course, three marinas, four boat clubs and a public boat ramp.

The Chesapeake & Ohio Canal National Historical Park, which follows the Potomac River from the District to Cumberland, Md., and preserves hundreds of canal structures such as locks, lock houses and aqueducts. The canal operated from 1828 until 1924.

National Capital Parks Central, incorporating the most famous of the capital's memorials and monuments: those to presidents Jefferson, Lincoln, Franklin Roosevelt and Washington, and to veterans of World War II, Korea and Vietnam. It also includes Constitution Gardens and Potomac Park, both on land dredged from the Potomac River, and such diverse sites as Ford's Theatre, the Peterson House (where Lincoln died), Pennsylvania Avenue Historical Park and the Old Post Office Tower.

National Capital Parks East, with 12 major park areas over 8,000 acres extending into Maryland, including Capitol Hill parks between Second Street and the Anacostia River (among them Lincoln, Folger, Stanton and Marion, as well as squares and triangles). Fort Dupont Park, with 376 acres, contains an earthenwork fort, part of the capital's Civil War defenses.

The park service oversees the George Washington Memorial Parkway and the Potomac Heritage National Scenic Trail, which currently comprises five individual trails. It also manages the Chesapeake Bay Gateways Network, 120 parks and other facilities in the Chesapeake watershed, which extends into Maryland, New York, Pennsylvania, Virginia and West Virginia.