The constructions of the Wiener Stadtbahn (built between 1894 and 1901) count among the highlights of the creative work of Otto Wagner (1841–1918) and occupy a special place within the history of modern architecture. For the first time, an urban means of mass transportation was conceived as an aesthetic object and systematically designed both in terms of art and architecture: from the viaducts and bridges to the stations and their decor. Wagner had recognized iron as the source material for a new architecture of the future and rendered the spectrum of its formal potential visible in the Stadtbahn. It became Vienna’s most imposing construction due to its unmistakable design, and thanks to its unsurpassed functionality it continues to influence regular (mass transit) life to this very day. On the 100th anniversary of Otto Wagner’s death, the volume pays tribute to the importance of the Stadtbahn in terms of architecture, urban space, and transportation; its local value for Vienna up to the present; and besides recent photographs by Nora Schoeller, it includes previously unpublished historical images and plans.