To step onto the Moscow metro is to step back in time and enter a museum of architecture and history. Opened 80 years ago -- on May 15, 1935 -- it is an extravagant gallery of communist design, featuring Soviet artworks, statues, chandeliers, stained glass, and ceiling mosaics. Built under Soviet dictator Josef Stalin, the metro now transports 7 million to 9 million people each day.