A couple of weekends ago, I picked up a SmartBike, threw it in my pickup and drove over to the National Arboretum for a couple of hours biking over there. It was very rewarding. (Columns from the Capitol, removed when they enlarged and refurbished it in the 1950s, are planted out here in the National Arboretum.)
I had never been there before. This 412-acre reserve off New York Avenue is on the northeastern edge of DC, just before you leave the District by way of the Baltimore Washington Parkway. Admission is free and there is plenty of parking.
It is well kept and features lots of little stands of different kinds of both indigenous and exotic trees. Hilly roadways snake through the grounds, and security is ever present. (A quiet spot in the National Arboretum.)
There were lots of picnickers on that Sunday. They were even having an ice-cream social there so I parked my bike among some green-thumb types, muscled ahead of some children on line and partook in a refreshing ice-cream cone.
Check it out someday. It's fun and relaxing.