Arlington National Cemetery

The Arlington National Cemetery is open to the public between 8am and 5pm.  The changing of the guard at the Tomb of the Unknown Soldier occurs every hour on the hour in the Fall, Winter, and Spring, and every half hour in the Summer. No reservation is needed.
For more information, visit
1 Memorial Dr, Arlington, VA 22202
It is located on the Metropolitan Washington D.C. Area Metrorail's Blue Line.