If you only have one afternoon in DC you should check out these museums as they are all within walking distance of one another.
The Smithsonian Butterfly Habitat Garden consist of four habitats:wetland,meadow,wood’s edge and urban back yard. There are as many as 30 species of butterflies. The Butterfly Garden is #FREE. For more details click this link.
Perspectves By: Ai Weiwei
May 12,2012-April 7,2013
This exhibition will display large scale installations,photography,video and architectural design of Ai Weiwei. The prolific and provocative artist used fragments from works that go back hundreds of years that effectively show a destructive and creative process in which he highlights the reality that we all live in midst of a world undergoing rapid and social transformations. This exhibit is #FREE. For more details click this link.
National Museum of African Art exhibits the finest traditional and contemporary art from Africa. This exhibit is #FREE. For more details click this link.