You could place it in DuPont Circle, if you need location ideas. If you are setting something in or near the White House, that would probably be the most realistic.
Chinatown and the area around it is interesting in my personal opinion. It's also walking distance from the White House.
If you want something more fancy and upperclass, than put it in Georgetown.
If you want something more business-y, you could put it in Arlington, VA. Which would be closest to the Pentagon.