I guess we’ve just naturally assumed for years that anything built underground doesn’t merit the artistic touch.  Certainly the DC subway is an engineering marvel, but bland, especially after all these years.  Unbroken visual uniformity and a utilitarian aesthetic.  I know the NYC subway system had a certain flair when it was built, some stations had strong decorative touches, but then it all got very run down.  It’s gone through a renaissance of sorts, especially in terms of the performing arts.  As you walk through the now much cleaner passageways, people performing music are everywhere.  DC is struggling to just keep up.  Lots of delays and obstructions due to long overdue repairs.  
The Swedish subway system is a marvel.  An innovative marvel.  No, I’ve never been to Sweden, but the images of that transportation system fire the imagination.  You can check out photos of this underground wonder at this site.  
All of this an excellent example of how a greater vision can be realized by dreaming big.  And hopefully an inspiration to never settle for “good enough.”