During the hearing at the very end of Winter Soldier:
Hearing General: Why haven't we yet heard from Captain Rogers?
Black Widow: I don't know what there is left for him to say. I think the rock in the middle of the Potomac made his point fairly eloquently.
Wikipedia tells me that the Potomac is the river in Washington, so I'm guessing that's something related to all the water around the Triskelion?
Can anyone explain this line properly for me?