This is right in the heart of DC.
Note that this is not the same as the Dupont Metro (subway) station, which is still in use. It's my understanding that DC used to have an extensive trolley system, but unlike most cities, decided to scrap it entirely when it built its subway system starting in the 1970s.
There's a short video and a couple of pictures. Unfortunately, not that many images of the abandoned station.
(This may require free registration.)