Smithsonian Institution - world's largest museum complex

The Smithsonian Institution is a group of museums, research centers, and a zoo administered by the U.S. government and is described as the world's largest museum, education, and research complex. It comprises 19 museums and galleries, the National Zoo, and numerous research facilities with collections totaling hundreds of millions of objects. The Smithsonian Institution Building (the 'Castle') on the National Mall serves as its administrative headquarters.