Location

Underground station Rotes Rathaus is directly adjacent to the reversing loop at Alexanderplatz that has existed since the 1930s. The latter runs below Rathausstraße and ends approximately level with Jüdenstraße.

The three entrance stairways of underground station Rotes Rathaus are directly in front of Berlin’s seat of government, while the station itself is located underneath Rathausstraße, between Spandauer Straße and Jüdenstraße.

Because the Alexanderplatz reversing loop will become a normal line section in the course of work, a new track-switching system will be linked to underground station Rotes Rathaus to the west of Spandauer Straße.

© Collignon Architektur
Design

Underground station Rotes Rathaus was designed by the Berlin-based architectural practice Collignon Architektur.

The idea was inspired by the roof vaulting of the medieval town hall in Berlin that was rediscovered during archaeological excavations. Seven centre columns support the majority of the roof load, their flared heads taking on the appearance of mushrooms reminiscent of the old vaulting. Combined with the single island platform, the concourse has a spacious, airy feel. In terms of colour, the station features a modern black and white design.

Underground station Rotes Rathaus is arranged over two levels: the platforms for the new U5 are found on the upper level, while the lower one will feature a storage siding as a replacement for the reversing loop at Alexanderplatz.

© bünck+fehse
Construction

The excavation pit for underground station Rotes Rathaus is built using the cut-and-cover top-down method. Diaphragm walls made of reinforced concrete initially provide support for the sides of the pit. Following this, a waterproof floor is constructed in the soil using jet grouting to form the bottom boundary of the pit. A cover is then concreted over the structure, minimising noise and dust pollution.

Inside the pit, the soil is excavated and the reinforced concrete floor and walls of the structure are built. A particular feature of underground station Rotes Rathaus is the fact that the pit cover is also the station roof. During its construction, the flared support heads will be concreted in at the same time. The heads of the supporting columns are thus structurally complete; the column sections will be built from below at a later point.

During preliminary works, the connection to the existing reversing loop at Alexanderplatz is also prepared, requiring the old, existing wall to be demolished. The surrounding soil will be frozen beforehand to ensure the necessary stability.

Once the basic structure is complete, finishing and completion is carried out: gravel is poured in, the tracks are laid and all technical cabling required for underground operation is installed. Lifts and escalators are also added. The interior design envisaged by the architects for the floors, walls and lighting is then completed. In a final step, typical facilities of an underground station such as ticket machines, ticket-cancelling posts and information displays are installed.

© PRG U5/Maik Kopsch
Archaeological finds

From early October 2009 to November 2011, 22 archaeology experts under the direction of archaeologists from the Berlin Monument Authority set to work in the area of the future construction sites for the U5 gap closure. Particularly extensive finds were unearthed around underground station Rotes Rathaus.

Acting with great care to uncover past treasures, the foundations and basement walls of the medieval town hall found by the archaeologists was just the start. Coins originating in East Prussia, Pomerania and Bohemia reveal a great deal about the city’s earlier economic life. The cellars of the silk factory in which the Jewish theologian and philosopher Moses Mendelssohn worked from the mid-18th century were discovered in Jüdenstraße. The most spectacular find was made during digs in the rubble of a house destroyed during the war, located on Königstraße (now Rathausstraße): eleven modernist sculptures previously thought to be lost.

Even though not every interesting discovery dates back to the Middle Ages, the archaeological excavations brought a great many valuable objects to light. Alongside a safe that was probably ‘buried’ in the final days of the war and still even contained half-burnt banknotes and documents, many coins and everyday items were uncovered.

Of the remains of the former town hall, which was structured in aisles like a church, two aisles were completely preserved. As a result, the position of underground station Rotes Rathaus and its entrances was redesigned, because one entrance would have been located directly in the area of the archaeological finds.

© Martin Stefke
Position of the new underground station Rotes Rathaus