I travel a little for work and have been sent to WA, DC a few times. The hubs had never been (which is an abomination, since he used to teach history to high schoolers), so he tagged along went I went last fall. And it. was. amazing. I saw the same sites as I've seen on my own, but it was a million times more fun with him.
Actually, renting bikes from a kiosk and riding around to see the monuments in the middle of the night was a new experience for me. And it was the most fun part of a really fun trip. Everything is more majestic all lit up at night.