This is an exceptionally well-appointed place for a visit to Washington DC. You can walk anywhere from here: Smithsonian/National Mall is about 10 minutes, the Capitol maybe 20, the White House, in the other direction, about the same.
It is a very nice building. I am a little uneasy with the requirement that you don't let anyone know it's an Airbnb but there was never a problem with the polite and courteous concierge, who handed over the keys with no questions. The apartment is spacious and airy, given its location, and well equipped: it has a washing machine and dryer, a large and well-equipped kitchen, and two bathrooms (most welcome as we had been sharing a single bathroom with our kids for the previous two weeks). There is a surprisingly good gym in the building. The apartment is filled with positive motivational messages...
Washington DC is one of those places where a walk of a couple of blocks can put you into a very different district with a very different feel to it; you do need to be aware when you're walking around. The area immediately around the apartment, though, is fine.
The closest museum is the Newseum, which I recommend very highly - and go now, because I believe it's moving in January. I'm still kicking myself that I didn't get to the National Archive, also very close.