Well, Jon, this is - indeed - very hard. Not even my sister, who has been to DC (which I take is mostly Washington DC, right?) can help me (that's where I am at present).
But I must say it is, in fact, Tom's turn to let us guess again where he was, for he was the one to guess Edinburgh right immediately - which I knew would not be difficult for anybody, since I chose the most touristy of all pictures I have for this game to give everyone a fair chance.
Bad piece of luck, Duck, if the wife has so many other plans for you right when there's a place that you, too, would have guessed at once, isn't it so?