The Kennedy Center

The Kennedy Center offers a free tour of the building and grounds every 10 minutes. No reservation is needed. Just visit their Tour Desk on the A Level of the Kennedy Center. A tour guide will be waiting for you.  
For more information, go here
2700 F St., NW, Washington, D.C. 20566
The Foggy Bottom/George Washington University Station on the Orange and Blue lines is the stop closest to the Kennedy Center.
From there it is a short walk via New Hampshire Avenue OR use the FREE Kennedy Center Shuttle (signs are towards the left as you exit the escalator). The shuttle departs every 15 minutes from 9:45 a.m.-Midnight Monday-Friday, and 10 a.m.-Midnight Saturdays, and noon-Midnight Sundays and 4:00 p.m.-Midnight on Federal  holidays.