Kenilworth Aquatic Gardens protects lotus ponds, waterlilies, marsh, and river-edge habitat along the Anacostia. It is the only National Park Service site devoted to aquatic plants, and it feels very different from the monumental core of Washington, D.C.
Come on an early summer morning if you can, when the waterlilies and lotus flowers are open and the heat has not yet settled in. Boardwalks and trails also make it a good birdwatching stop.