The Washington Metro, known colloquially as Metro and branded Metrorail, is the heavy rail rapid transit system serving the Washington metropolitan area in the United States. It is administered by the Washington Metropolitan Area Transit Authority (WMATA), which also operates Metrobus service under the Metro name. Besides the District of Columbia, Metro serves several jurisdictions in the states of Maryland and Virginia. In Maryland, Metro provides service to Montgomery and Prince George's counties; in Virginia, to Arlington and Fairfax counties and the independent city of Alexandria. Combined with its ridership in the independent Virginia cities of Falls Church and Fairfax, the Metro service area is largely coextensive with the inner ring of the Washington metropolitan area. The system is currently being expanded to reach Dulles International Airport and Loudoun County, Virginia. It operates mostly as a subway in the District itself, while most of the suburban tracks are at surface level or elevated.