What is the name of the 4.2 acre public garden in the Smithsonian complex, adjacent to the Smithsonian Castle on the National Mall in Washington?
National Mall The National Mall is a national park in downtown Washington, D.C., the capital of the United States. The National Park Service (NPS) of the U.S. Department of the Interior administers the National Mall, which is part of its National Mall and Memorial Parks unit.
United States Botanic Garden The United States Botanic Garden (USBG) is a botanic garden on the grounds of the United States Capitol in Washington, D.C., near Garfield Circle. The U.S. Botanic Garden is supervised by the Congress through the Architect of the Capitol, who is responsible for maintaining the grounds of the United States Capitol. The USBG is open every day of the year, including federal holidays. It is the oldest continually operating botanic garden in the United States.