Union Station - St. Louis, MO
Opened in 1894, Union Station was designed by St. Louis architect Theodore C. Link in the Richardsonian Romanesque style.  There are also touches of the French Renaissance.  You can also detect a hint of  King Ludwig II's Neuschwanstein castle in the tower.  The train sheds were designed by George H. Pegram.  Union Station quickly became one of the world's busiest railroad stations, handling over 100,000 passengers daily in its heyday.  The station closed in 1978, but was reborn in 1984 as a hotel and "urban marketplace."
The two photos immediately above and the one at right are were taken in the lobby of the new luxury hotel.  This was the main waiting room of the original station.  The picture below shows the new mall behind the hotel in the former train shed.  The remainder of the shed is comprised of an artificial lake (part of the hotel) and a parking lot.