The Blue Line is one of the four subway lines of the Massachusetts Bay Transportation Authority. It extends from Wonderland Station in Revere in the north to Bowdoin Street near Beacon Hill in Boston in the south. It meets the Green Line at Government Center and the Orange Line at State Street. It also provides mass-transit service to Logan International Airport. The line is designated "Blue" because for much of its length it uses the old Boston, Revere Beach & Lynn Railroad right-of-way along the seacoast in Revere and East Boston, and the tunnel to East Boston runs under the Atlantic Ocean. Boston's Blue Line was the first subway in the world to run underneath a section of the ocean.