The National Mall and the monuments
The big lawn that runs from the Capitol to the Lincoln Memorial, lined with museums and monuments. It's free and open day and night. It's also nearly two miles long, which surprises everyone.
Don't try to walk it end to end with little kids. Pick one end per day, and walk the memorials in one direction only, so you don't have to come back. The Lincoln Memorial, the Reflecting Pool, and the World War II Memorial sit close together at the west end.
The best tip of all: see the monuments at night. They're lit up, the heat of the day is gone, and the crowds are much smaller. The Lincoln Memorial after dark is the picture your kids will remember.
Tip: Free and open 24 hours. Walk one end per day, one direction only. Come back at night for the lit-up memorials.
