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Washington, D.C., in the United States, is located at (the coordinates of the Zero Milestone, on the Ellipse). According to the United States Census Bureau, the city has a geographical area of , of which is land, and the remaining (10.16%) of which is water. Washington is surrounded by the states of Virginia (on its southwest side) and Maryland (on its southeast, northeast, and northwest sides); it interrupts those states' common border, which is the south shore of the Potomac River both upstream and downstream from the District. The portion of the Potomac River that passes Washington is virtually entirely within the District's border, as the District extends to the south bank. The city contains the historic "federal city", the territory of which was formerly part of those two adjacent states before they respectively ceded it for the national capital. The land ceded from Virginia was returned by Congress in 1847, so what remains of the modern District was all once part of Maryland. ==Topography and geology== The topography of the District of Columbia is very similar to the physical geography of much of Maryland. The District has three major natural flowing bodies of water: the Potomac River and two tributaries, the Anacostia River and Rock Creek. The confluence of the Potomac and Anacostia forms the historic peninsula known as Arsenal Point. The District also includes the Washington Channel, which flows into the junction of the Anacostia and Potomac rivers. There are also three man-made reservoirs: Dalecarlia Reservoir, which crosses over the northwest border of the District from Maryland, McMillan Reservoir near Howard University, and Georgetown Reservoir upstream of Georgetown. A fourth, minor reservoir is at Fort Reno in Tenleytown. The highest point in the District of Columbia is 410 feet (125 m) above sea level at Reno Reservoir in Tenleytown. The lowest point is sea level, which occurs along all of the Anacostia shore and all of the Potomac shore except the uppermost mile (the Little Falls-Chain Bridge area). The sea level Tidal Basin rose eleven feet during Hurricane Isabel on September 18, 2003. The geographic center of the District of Columbia is located near 4th Street NW, L Street NW, and New York Avenue NW, not under the Capitol dome as is sometimes stated. (The Capitol does mark the intersection of the District's four administrative quadrants.) Other prominent geographical features of Washington, D.C., include Theodore Roosevelt Island, Columbia Island, the Three Sisters, and Hains Point. Some areas, especially around the National Mall and parts of Foggy Bottom, were marshes or parts of the river that have been filled in. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Geography of Washington, D.C.」の詳細全文を読む スポンサード リンク
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