United States Capitol Visitor Center

The United States Capitol Visitor Center (CVC) is a large underground addition to the United States Capitol complex which serves as a gathering point for up to 4,000 tourists and an expansion space for the U.S. Congress. Opened in 2008, it is located on 1st Street East below the landscaped tree-shaded grounds of the East Front of the Capitol and included the development of the surface plaza (which formally served as a parking lot since the mid-1920s).

Source: Wikipedia — United States Capitol Visitor Center (CC BY-SA 4.0)