Greater Greater Washington has a great article about the Metro’s 17-foot long “experimental station” (photo above) built in 1968 to test the design of Chicago architect Harry Weese.

Architecture Week has a quick overview of the station mockup, and the whole history is worth your read:

Prior to construction, the NCTA erected, on a site adjacent to the future Rhode Island Avenue station, a partial full-scale mock-up of a cross section of a typical below-grade vaulted train room, complete with a segment of a full-size train car. The model measured 64 feet (19.5 meters) in width, 30 feet (9.1 meters) in height, and 17 feet (5.2 meters) in length and was used to study and test various components of the design and construction of the system.

I love the Washington Metro stations: they have aged very well in the last 40 years and are an iconic statement which is instantly recognizable as being DC.