Vienna
Vienna began trial service on its U-Bahn in 1976, when the U4 started running on converted tracks of the old Stadtbahn, and in 1978 the U1 opened through the first newly dug tunnel. The U6 still runs on the Stadtbahn viaducts that architect Otto Wagner began building in 1898, through many of the stations he designed. In the nearly fifty years since, the network has kept growing. The U2 reached the new Seestadt district in the northeast in 2013, and in 2012 the city introduced an annual pass for 365 euros, a euro a day.
