At least half the time I flew into DCA we came up the Potomac. You either had a view of Alexandria or Maryland, and the Capitol bldg, monuments, etc. were waaay in front of you; no real view at all.

When we arrived from the north, we used to fly in over the capitol, and you had a good view of the buildings, Pentagon, etc. from the right side. I think they've restricted the approaches, now, so maybe the left side is the better side.

OTOH, I used to fly into BWI a lot, too (cheaper ) and you saw nothing from there.

So, the bottom line is, if you're coming in from the north/west, you have a 50-50 chance of flying where you can see the buildings. I believe the left side is the best, but I haven't flown there since 9/11, so maybe somebody has more definite advice.