My only real "must see" on my recent trip to Washington DC was the Pandas at the National Zoo (I only had one free day on the trip.) When I first arrived at the Zoo the "baby" (who is now about 60 pounds) was up a tree munching away and ignoring the world. Later she was was down with mom enjoying a snack in the afternoon sun. I took the hint and had lunch at a nice sidewalk cafe down near the Metro stop. I can't wait to go back.