A map of Vienna’s city rail network in 1933, showing the extensive tram (Strassenbahn) network and the Wiener Stadtbahn, which now forms part of both the U- and S-Bahn networks. Interestingly, the stations of the Stadtbahn are only denoted by two-letter abbreviations on the map, which have to be cross referenced with a legend at the top right. This is also probably one of the earliest attempts at indicating fare zones I’ve seen on a transit map.

Source: David Rumsey Map Collection