We spent our first full day (Saturday) in DC wandering around the National Mall. The Mall is boxed in by the Capital Building and Washington Monuments on the ends, and the Smithsonian Museums along the long edges. We did visit the Freer, Sackler and African Art Galleries, as well as a quick stop in the Castle, but the highlights to me were the gardens hidden among the museums.
The Ripley Garden is really a cut through between the Arts and Industries Building and the Hirschhorn Museum from Jefferson Drive (along the Mall) to Independence Avenue. It's really lovely garden with a fountain, a variety of raised beds, and a number of container plantings. The photos below are actually taken from two different times that day, earlier in the morning during a driving rain, and then later when things had begun to dry out.
Highlights of the Ripley Garden: