Hirshhorn has comfortable chairs to view the works of Calder and de Kooning. Check out this place to find the answer to that question and more. Both the Sackler and the Freer offer unusual Asian artwork. The Castle offers a nice history and overview of the Smithsonian Museums. Natural History .
Natural History has the dinosaurs and gems.
The Smithsonian station puts you right in the middle of the National Mall and numerous signs point out which building is which. Remember, The National Gallery of Art is also on the Mall but not managed by the Smithsonian. For the purist, the National Gallery of Art offers 2 buildings of collections in a calm and relaxing environment. The National Air and Space and American History Museums have cafeterias. I'd just as soon settle for the ubiquitous street vendor who offers hot dogs, chips, pretzels and beverages for a quick and cheap fix.