The history of the subway line U7 actually begins with the construction of an additional track section of the line U6 in 1924 to 1930 leading from the station Mehringdamm to Neukoelln. This short route was later continuously extended toward the south to Rudow from 1959 to 1972 and to the north to Rathaus Spandau in 1966 to 1984 .

 

All subway lines built from 1923, are known as wide gauge.

 

The wide gauge contains wider tunnels as well as wider, longer and higher subway cars in addition to a different power supply from the narrow gauge. The subway cars obtain the driving current from the live rail and feed back via the driving rail. The live rail is contacted on the lower side. The polarity is negative. (narrow gauge - live rail contacted on the upper side, polarity positive).

 

One thing the wide gauge shares with the narrow gauge: The track is the railway typical "normal track" of 1435 millimetres.