I was in DC for a conference, and had very little time to wander about; I would have loved to go along the tidal basin and see the trees. My conference was at the Omni Shoreham and these trees were within walking distance from the hotel.
By the way, did you know that on the DC Metro, the trains can open, pouring a huge mass of humanity out on the platform, but then close before any people are allowed onto the Metro, but long enough for the doors to close on and grab your jacket? It helps to have a few strong hands among fellow passengers who pried the door back open while I did this little tugwar maneuver pulling my jacket back, or I'd have had to return to North Dakota winter-jacket-less. Just thought you'd like to know.