Stuttgart 21 takes Paul Bonatz’s 1928 terminus, one of Germany’s landmark railway buildings, and converts it into an eight-track underground through-station. The structural centrepiece is a single concrete shell roof, 450 metres long and 80 metres wide, carried on 28 chalice-shaped columns that each span about 32 metres, with the shell only 40 centimetres thick at midspan and daylight entering through a light eye at the top of each chalice. Ingenhoven Associates won the competition in 1997 working from a concept by Frei Otto; Ed. Zublin built the underground station. Around it sit roughly 57 kilometres of new railway and 30 kilometres of tunnel, and the whole thing frees about 100 hectares of railway land in the middle of the city.
Project Scope
Conversion of a 16-platform terminus into an 8-track underground through-station beneath the retained 1928 Bonatz building.
About 57 kilometres of new railway, including roughly 25 kilometres of high-speed line, and about 30 kilometres of tunnel.
Station hall 450 metres by 80 metres on 28 chalice columns spanning about 32 metres each; shell 40 centimetres thick at midspan; clear height 8 to 12 metres.
A 6.5-metre level change from the south to the north end of the platforms.
New Filder route, airport station and Neckar crossings within the wider programme.
Releases about 100 hectares for the Rosenstein district and Europaviertel.
Why It Matters
The shell roof is one of the few pieces of genuinely ambitious concrete engineering built in Europe this century. A 40-centimetre shell over a 450-metre hall is a geometry problem before it is a structures problem, and the formwork and pour sequencing for the chalices are the reason the station structure alone has taken more than a decade.
The cost record is the other story and there’s no polite way around it. The estimate was €2.8 billion in 2007, €9.15 billion in 2022, and €14.5 billion as of June 2026. The new Hauptbahnhof is scheduled for December 2031, with associated works phased to 2033. Stuttgart 21 is now the reference case in German infrastructure for what happens when a project’s scope, its funding partners and its political cover are all fixed before its ground conditions are known.
Project Team & Details
| Developer | DB Projekt Stuttgart-Ulm GmbH |
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| Owner / Client | Deutsche Bahn AG (DB InfraGO) |
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| Architect | Ingenhoven Associates (concept by Frei Otto) |
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| General Contractor | Ed. Zublin AG (STRABAG) |
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| Major Subcontractors | Rhomberg Bahntechnik (Rail Systems)
DB Bahnbau Gruppe (Rail Systems) |
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| Status | Under Construction |
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| Delivery Method | Design-Bid-Build |
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| Funding Source | Mixed |
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