The United States Botanic Garden is the national conservatory beside the Capitol, with extensive plant collections under glass. The jungle room's canopy walk is a highlight, and the warm, humid conservatory can be a welcome change of pace during a long day around the National Mall.
Bartholdi Park, just south of the conservatory, adds a quieter outdoor stop centered on the Bartholdi Fountain. Together they make one of the Mall area's best low-stress breaks between the large museums and monuments.