Digging through the heart of reunified Berlin: Unbundling the story of the Tiergarten-tunnel mega-project

The Berlin Tiergarten tunnel project consisted of a joint planning approval procedure for one road and several rail tunnels (inter-city, metro rail and city subway). The tunnels lead through the heart of re-unified Berlin, starting at the site of the new Central Railway Station, cutting underneath the River Spree and the new Federal government quarter, as well the Tiergarten park and the new entertainment complexes at Potsdamer Platz. This paper traces the decision-making processes for this crucial post-Berlin Wall mega-project, and raises important questions regarding optimistic forecasting, the estimation of risk, cost overruns, the role of prestige in large infrastructure projects, and the limits of public review procedures. More importantly, it provides particular insights into a complex, highly consequential case where multiple urban transport mega-projects were bundled together for joint approval and implementation.