Arlington Cemetery
This was a neat experience -- the kids didn't fully appreciate it, but they enjoyed being there for the most part. 
Unbelievable how many people are buried here -- thousands upon thousands. It was really a touching experience. 
Even more headstones -- reminders of past heroes and good men and women who served faithfully in past wars to ensure others could enjoy basic rights that so many are deprived of, even today. 
It was good to see the Pledge of Allegiance (since you do not see it in schools or anywhere else these days). 
Lost, but not forgotten - Tomb of the Unknown Soldier. This was something we did not have time to see, but expect to go back and see. 