Dear PoPville – Unique DC tours/activities?

Photo by PoPville flickr user jennverr

Dear PoPville,

I’ve got a lot of family coming into town for the holidays this year and am wondering if you had any suggestions regarding something fun and different we might be able to do. For instance, they live in San Francisco and one of our favorite things to do when I visited was to complete a chapter of the now defunct Jejune Institute game (see here for details). I’ll be hosting during the Christmas week this year and would love to hear about something we could do beyond looking at the monuments.

We looked at some fun things to do here and here. Can you think of any other fun recommendations for this time of year?