The locations are fairly accurate, but they took a few liberties with their placement. For instance, Olney is actually south of Germantown rather than more to the north. Arlington National Cemetary is north of the Pentagon/Citadel rather than to the south/west. But places like Falls Church, Bethesda, Wheaton, Foggy Bottom, DuPont and the general path of the Potomac River are all fairly accurate.
Honestly, go to Google Maps and search for Washington DC and see for yourself. A lot of the downtown area is very well done.
i went there after i had the game go to the jefferson memorial youll find a little door to the basement
o and my hotel was in Bethesda my friends thought that was funny