Thanks to you all. Should be very helpful. I haven't found the Citadel or Farragut Metro before. And I've beaten my head against the walls of rubble trying to get to Dukov's Place.
So, just to be clear -- I need to cross the river, head south, and then re-cross it?
To get to Farragut Station, just cross that bridge near the Super Duper Mart and go a little bit south from there. Continue going south and you'll get to Dukov's Place. Keep going and you'll end up in Rivet City. And no, you don't have to recross the river. Rivet City is on the same side as both Farragut Station and Dukov's Place.
PS: Farragut Station is an important one to uncover. If you go inside, you'll find a path that will take you to Chevy Chase, which will lead you to the GNR building. It's the shortest route to get there AFAIK.