We stopped off at the Smithsonian Castle. This was the original Smithsonian museum. It has a lot of info about all the various museums.
We spent a couple of hours see all that stuff.
We then went on a bus to the second Air & Space Museum out at Dulles Airport where we spent a couple more hours.
We rode a bus back to the museum on the mall where we got back on the metro to our hotel. After a short rest, we walked to the Chinatown area down the street for dinner. Now we are back in for the night (8:15pm EST).