Although many visitors pass through Union Station on their way to Pittsburgh with Amtrak, few are aware of its enormous historical significance. The station -- also known as Pennsylvania Station or Penn Station -- was one of several passenger rail stations that Pittsburgh used during the 20th century and is the only one surviving.⠀ .⠀ The station building was designed by the famous Chicago architect Daniel Burnham, also responsible for the construction of the 1893 Chicago World's Fair and its historic White City. The station was built between 1898 and 1904, and featured the iconic rotunda. The feature can be seen as a remnant of the building's nineteenth-century history, as the rotunda was used as a sheltered turning space for carriages while passengers watched from above in the waiting room. The rotunda itself is listed on the National Register of Historic Places.