The City Hall subway station in New York City was built to be beautiful, as a showcase for the entire train system. But it was closed in 1945. However, passengers on the 6 train can see it if they don't disembark on the last stop -the train turns around in the closed station. If you're not in New York, you can see it in pictures at Jalopnik. Link -via Evil Mad Linkblog
(Image credit: John-Paul Palescandolo, Fred Guenther)