The extension to Niendorf was later realized in two stages: in 1979, work began on the line and the Hagendeel and Niendorf Markt stops, which were opened on June 2, 1985. In order to connect the new housing developments that had been built in the mid-1980s to the subway network, the extension around the stops Joachim-Mähl-Strasse, Schippelsweg and Niendorf Nord was started. The section went into operation on March 9, 1991.

Under construction: The Hagendeel stop, 1984

In 1983, interior work on the Niendorf Markt stop is in full swing

The gap closure

At the same time, construction work was also carried out on the inner-city section, which was a major technical challenge due to the densely built-up area. Since the new line at Berliner Tor had to be connected to the subway network from both directions without any crossings, a new four-track tunnel station was built here. After two years of construction, the northern platform could be used for the Ring Line from May 1964, then work began on the southern platform and the demolition of the old Ring Line stop.

In 1965, work began on the section between Schlump and Berliner Tor with the excavation of the starting shafts at the main station and Karolinenstrasse, from where the shield tunnelling machines dug their way deep under the city center, virtually toward each other. While digging was going on in front, the ring-shaped tunnel was being built right behind it. The stops were also laid out in a ring. The stops at the main station and Jungfernsteig were designed with four tracks in anticipation of further subway extensions. The extension of the Jungfernstieg stop was particularly difficult: protected by sheet pile walls, it had to be built openly in the Alster.

The inner-city line was commissioned in sections: The line between Berliner Tor and Hauptbahnhof went into operation on September 29, 1968. Here, the U21 ran from the main station via Berliner Tor to Barmbek. The U22 ran between Schlump and Gänsemarkt from May 31, 1970. On June 3, 1973, the extension at Jungfernstieg was completed and the entire line from Stellingen to Merkenstraße could be operated continuously.

Drilling under the city center - part of the shield tunneling machine, 1965

Interior of the Messehallen stop built according to plans by architect Otto Kindt, 1970

Stop additions

As the structure of the city and its population changed over time, stops were added to the existing subway network to ensure optimum accessibility and public transport connections. For example, the Kiwittsmoor stop went into operation on May 10, 1960, to improve accessibility to nearby hospitals and new housing developments. The Sengelmannstrasse stop, on the other hand, which opened on September 26, 1975, was intended to improve access to the City Nord office district. At the Garstedt stop, which went into operation on June 1, 1969, there was an interchange between the subway and the A2 trains of the Alsternordbahn, which significantly improved access to the surrounding area. The later extension to include the Richtweg and Norderstedt-Mitte stops, which opened on September 28, 1996, also significantly strengthened the connection to the surrounding area by providing a direct AKN connection in Norderstedt.

The new Garstedt stop around 1969

View of the platform of the Sengelmannstraße stop, around 1975

U4 Expansion

A central subway link was planned from the outset in the development of HafenCity, and construction officially began on August 23, 2007. In 2008, work began in an open excavation pit on Jungfernstieg, which also required reconstruction of the jetty for the Alster ships. The information pavilion there gave interested parties a variety of insights into the extensive project. At Berliner Tor, the U2 and U3 lines were also swapped and the station was thoroughly refurbished. For 15 months, tunnel borer V.E.R.A. dug its way from HafenCity to Jungfernstieg, where it arrived on November 7, 2009 - the first tunnel tube consisting of around 13,000 segments was completed. Starting again from the launch shaft in Versmannstrasse, the second tube of the 2.8km tunnel was then dug and finalized by January 2011. At the same time, interior work began on the tunnels and the two stops at Überseequartier and HafenCity University, so that the tunnels could be connected to the Jungfernstieg stop on February 28, 2011. The U4 was then officially inaugurated on November 28, 2012 and went into regular service at the timetable change on December 9, 2012.

Work on the U4 extension to Elbbrücken began as early as 2013. The subway stop of the same name then went into regular service on December 9, 2018.

View of the U4 construction site at Jungfernstieg, 2012

U4 tunnel drill V.E.R.A, 2012

Technical development

The history of HOCHBAHN was not limited to the construction and opening of subway lines and bus routes. There were also numerous developments in vehicle and operating technology. New vehicles and drive technologies were just as much an expression of HOCHBAHN's innovative ability as modern means of communication between the control center, drivers and passengers. The picture gallery provides a brief insight.