Design Boom has a huge gallery of the most beautiful works of subway station and tunnel architecture across the world. Pictured above is the Solna Centrum metro station in Stockholm, which opened in 1975. Shades of red dominate the artwork of the station, which depicts the social concerns of 1970s Sweden.
http://www.designboom.com/weblog/cat/9/view/8346/subway-architecture.html via Fast Company | Photo: flickr user Erwyn van der Meer, used under Creative Commons license