The best of the Best of Nature in DC is not the Japanese flowering Cherry trees at the Tidal Basin. For one thing, the Cherry blossoms are best seen against a blue sky. We lived in DC for 20 years, and only saw the Cherry blossoms against a blue sky 4 times. Clouds are white. Most of the Cherry blossoms are white. White on white does not impress. The #1 display of nature in DC is Azalea (and Rhododendron) season, roughly the middle of May. Small plantings of Azaleas are all over the place in downtown DC, but the best display are found in a number of specialized Azalea gardens: the National Arboretum; McCrillis Garden in Montgomery County, MD; the Montgomery Co. garden in northern Silver Spring; the grounds of a private school in the Montgomery County, MD, suburbs.
The Azaleas are the best of the best. For the rest of DC Nature, in no particular order:
The Bridge and River tour is a scenic 3-hour bicycle tour will take you from the Upper West Side of New York City up and over the George Washington Bridge for a ride along the river on Route 9W. Get the full touring experience and leave New York City for a few hours. During the ride, we make stops at Grants Tomb Memorial on the Upper West Side.