The most striking thing about bicycles in the Capitol is that there really is something for everyone, the bicycles don't fall into one tribe. I found the diversity refreshing.
From the fixed gear in Dupont Circle:
The symphony in blue and purple on the National Mall:
A hybrid with a seat shaped like a cow near the Embassies:
A luscious purple cruiser in Georgetown:
Tricycle parking in Georgetown:
and and unrelated Mama Chariot in Georgetown:
A basket bike in Dupont Circle:
Raleigh 3 speed in Dupont Circle (with a nicely attached modern tail light):
A pennyfarthing at the Smithsonian:
And my favorite, a singlespeed designed and manufactured by the Wright Brothers, which helped to finance their dabblings in aviation.