The Wiener Stadtbahn (German for "Vienna Metropolitan Railway") was a public transportation system operated under this name from 1898 to 1989. Today, the Vienna U-Bahn lines U4 and U6 and the Vienna S-Bahn (rapid transit) run on its former lines. The name derives from the usage of the term around the turn of the 19th/20th century to denote a full-scale railway in an urban area, separated from all other forms of traffic. It is not related to the usage of the term Stadtbahn in post-WWII Germany. The Stadtbahn is one Vienna's better known examples of early Art Nouveau architecture. Its most famous buildings are the two former station entrances on Karlsplatz, now used as a café and a museum respectively, and the Hofpavillon, a station built specifically for Emperor Franz Joseph, located at the eastern end of Hietzing station. Other preserved historical stations are the elevated stations along the Gürtel and in some of the suburbs.