Elongated, silver, reflective object hovering over Capitol

I exited my hotel on School St with a co-worker. Upon looking up, I saw a thin, roughly cylindrical looking object in the sky. The object was oriented vertically and was silvery looking. It was silver in color and was occasionally glinting in the sunlight. It was not an airplane, and reminded me of a long, skinny mylar balloon. I pointed it out to my coworker, and he made a similar observation, but was relatively uninterested. Based on the surrounding buildings and the viewing angle, I would estimate it was between 2000 and 8000 ft. I cannot say with certainty how long it was, but would estimate maybe 20-30 ft and a couple feet in diameter. Its long axis was vertical. Of course, if the object was really high, it could have been the size of an aircraft fuselage.
The day was spectacularly clear and beautiful. The sky cloudless and winds calm.
Per consulting a map, it was approximately directly above the US Capitol Building.
I can accept that this was probably a balloon. I am sure it was adequately checked out and evaluated by the authorities . But, I wanted to report it mainly because of where I saw it.