In 1927, construction started on a subway line underneath Große Frankfurter Straße (now Karl Marx Allee). Line E as it was named, first opened on December 21, 1930 with 12 stations running from Alexanderplatz to Friedrichsfelde. This line was the only one that fell entirely in the Eastern side of a divided Berlin. In the early 1970s the line was extended to Tierpark. In the late 1980s, the line was extended even further to Hönow, which is currently the eastern terminus of the U5 line.
After German reunification, it was decided that the line should be refurbished. Portions of the train rails that were still in use dated back to the original 1930 construction. In 2003, the remodeling began and the original tile walls were pulled down. Unfortunately, someone decided to have them replaced with large colorful enamel plates rather than the charming tile of the past. While they may be more resistant to vandalism, the old world charm that once existed there has definitely left the station(s).
Quiet and comfortable, the U5 is one of my favorite lines, although once it gets past Tierpark, the line goes above ground and it feels more like the S-Bahn than the underground. The stations from the original construction all have exposed iron work from the 1920s.
Alexanderplatz
Schillingstraße
Strausberger Platz
Weberwiese
Frankfurter Tor
Samariterstraße
Frankfurter Allee
Magdalenenstraße
Lichtenberg
Friedrichsfelde
Tierpark
Biesdorf-Süd
Elsterwerdaer Platz
Wuhletal
Kaulsdorf-Nord
Neue Grottkauer Straße
Cottbusser Platz
Hellersdorf
Louis-Lewin-Straße
Hönow