also ferries and water cruises that cross the Potomac River. One of these is the Potomac Water Taxi, operated by Hornblower Cruises, which goes between the Georgetown Waterfront, the Wharf, the Old Town Alexandria Waterfront, and National Harbor. Rail The Washington Metropolitan Area Transit Authority (WMATA) operates the Washington Metro, the city's rapid transit rail system. The system serves Washington, D.C. as well as its Maryland and Virginia suburbs. Metro opened on March 27, 1976, and consists of six lines (each one color coded), 97 stations, and of track. Metro is the second-busiest rapid transit system in the country and fifth-busiest in North America. It operates mostly as a deep-level subway in more densely populated parts of the D.C. metropolitan area (including most of the District itself), while most of the suburban tracks are at surface level or elevated. Metro is known for its iconic brutalist-style vaulted ceilings in the interior stations. It is also known for having long escalators in some of its underground stations. The longest single-tier escalator in the Western Hemisphere, spanning , is located at Metro's Wheaton station in Maryland. Union Station is the city's main train station and serves approximately 70,000 people each day. It is Amtrak's second-busiest station with 4.6 million passengers annually and is the southern terminus for the Northeast Corridor and Acela Express routes. Maryland's MARC and Virginia's VRE commuter trains and the Metrorail Red Line also provide service into Union Station. Following renovations in 2011, Union Station became Washington's primary intercity bus transit center. Although Washington was famous throughout the 19th and early- to mid-20th centuries for its streetcars, these lines were dismantled in the 1960s. In 2016, however, the city brought back a streetcar line. The DC Streetcar consists of a single line in Northeast D.C., along H Street and Benning Road, known as the H Street/Benning Road Line. Bus Two main public bus systems operate in Washington, D.C. Metrobus, operated by WMATA, is the primary public bus system in Washington, D.C. Serving more than 400,000 riders each weekday, it is one of the nation's largest bus systems by annual ridership. The city also operates its own DC Circulator bus system, which connects commercial and touristic areas within central Washington. The DC Circulator costs only $1 to ride and is composed of six distinct routes that cover central D.C. and suburban Rosslyn, Virginia. The DC Circulator is run via a