Every year millions of people visit Washington, D.C., and the Smithsonian Institution, which includes the National Air and Space Museum and the National Portrait Gallery among the sections of the multifaceted complex, but they don't see everything there is to see. In this series, actor Tom Cavanaugh takes viewers behind the scenes of the tourist attractions and into the private rooms, high-tech vaults and cutting-edge research labs that aren't part of the museums' regular tours. Cavanaugh reveals artifacts and rarely seen treasures that visitors miss. The show discusses each object's origin, how it is being preserved and studied, and what each thing might tell us.