Frank Herfort spent five years photographing as many Soviet era subway stations as possible (and permitted). Herfort has a book coming out CCCP Underground. These are taken from
this article in the New York Times.
Komsomolskaya Station, Moscow.
Nizami, Baku, Azerbaijan.
Botanicheskaya,Yekaterinburg (where the czar and the royal family were slaughtered).
My personal favorite, Kyivska, in Kharkiv, Ukraine.