The Washington Metro is comparable to the S-Bahn. DC doesn't have a system comparable to the Berlin Metro, because it doesn't have the dense tenement neighborhoods to support such a system.
The DC metro area actually has more population than the Berlin metro area. Most of it is just built in sprawling postwar American style, though it's urbanizing more than many equivalent American cities.
The DC metro area actually has more population than the Berlin metro area. Most of it is just built in sprawling postwar American style, though it's urbanizing more than many equivalent American cities.