From an Eastern Branch to an Independent Line
The early name of Berlin’s U5 was Line E. Running east from Alexanderplatz through Frankfurter Allee and Lichtenberg to Friedrichsfelde, it brought eastern neighborhoods into the city-center underground network. The elevated railway company had obtained permission for an eastern extension in 1914 and envisaged a branch of an existing line. War and postwar difficulties prevented this plan from being realized in its original form.
Berlin subsequently chose an independent line, avoiding the convergence of two eastern passenger flows on the existing trunk route. It also adopted larger vehicles and tunnel cross-sections. The eastern end extended beyond the original limits to land where a depot could be built. Passenger connections, existing line capacity and maintenance space all shaped its route.
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Municipal Transport and the 1930 Opening
Berliner Verkehrs-Aktiengesellschaft, or BVG, began operating on January 1, 1929, following the merger of the underground, bus and tram operators. Line E thus entered an integrated municipal transport system. On December 21, 1930, its ten stations between Alexanderplatz and Friedrichsfelde joined the network together.
The 1930 route connected eastern neighborhoods directly to Alexanderplatz and its other urban rail services. Sections toward Hönow and the central station were added to this corridor in later decades.
An Underground Interchange at Alexanderplatz
The central end of the line involved a complex reconstruction of the station. Berlin’s heritage survey dates construction of the Line E station to 1927–1930 and records the participation of architect Alfred Grenander and engineer Johannes Bousset, with the city as client. Underground works had to be coordinated with existing stations and buildings on the square, accommodating both train operations and interchange space.
Line E’s four-track station hall lay at a deeper level, below the lines later numbered U2 and U8. The passage system completed in 1930 connected the different halls, with stairs and intermediate levels carrying transfer passengers. Green glazed wall tiles and exposed riveted steel columns became architectural features of the interchange. Passengers could change lines underground without returning to street level each time.
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Everyday Work at the Depot
The Friedrichsfelde depot entered service with Line E in 1930, providing train storage and maintenance at the eastern end. Its sheds and servicing facilities formed part of the infrastructure that kept passenger services operating.
Space was also reserved for expansion. Bousset’s 1935 engineering book described the facilities and plans for further development. Sheds and workshops evolved with traffic volumes and maintenance requirements.
References: [1]
Extending East and Connecting the Western End
After the war, the route continued to develop in East Berlin. It reached Tierpark in 1973, with further sections toward Hönow opening in 1988 and 1989. Much of the later extension ran above ground. As the eastern terminus moved outward, the service pattern originally centered on Friedrichsfelde changed.
The western connection belonged to another phase of construction. PORR built Rotes Rathaus station for BVG, completing the excavation, station structure and links between old and new tunnels from 2013 to 2016. Work then continued on the existing four-track tunnel and station fit-out. When the western extension entered regular service on December 4, 2020, passengers could travel from Hönow through Alexanderplatz directly to Berlin’s central station without changing trains.
The Through Route and Later Station Opening
Completion of the through route at the end of 2020 did not mean that every new station was receiving passengers. Museumsinsel opened on July 9, 2021; trains had previously passed through without stopping. Its platforms lie below the Spree Canal. Workers froze the ground to protect the excavation, creating a frozen body of about 28,000 cubic meters with brine cooled to minus 37 degrees Celsius.
From the eastern route of 1930 through later suburban additions to the underground connection across the city center, U5 underwent repeated construction under different conditions. Sections and stations entered service in stages, gradually forming its east–west corridor.