Deeper than Porter Square?
Maybe a bit less, but it's one escalator straight down, and they say some of the other Metro stations are even deeper.
Which one was used in The Heavenly Kid?
And are either of them as long as the escalator to the New Line in Tokyo?
Woah.
The deepest I remember was Rosslyn, the hub in Georgetown, which is right next to the Potomac and hence deep enough to run beneath it. My best estimate based on the length of the escalator put it 14 stories deep. Rosslyn had some 3 escalators running up and 3 down, though, because it was a hub, so I can't tell by looking which station you're in, but I bet it was fairly close to the river.