The underground addition to Gothenburg Central Station, known locally as Centralen, is part of the ground-breaking West Link project. The new station will markedly increase the region’s rail capacity, and provide rail users with greater freedom and comfort. Alongside the complexities that come with designing an underground station in the heart of a big city, the soft Gothenburg clay added an extra challenge, as structures can settle by more than a metre if no preventative measures are taken. Once complete, the new Centralen station will be transformational for Gothenburg and the Västra Götaland region, one of the fastest growing regions in Northern Europe . The design stage commenced in 2016 and the first construction stage kicked off in 2018. A major milestone was reached in 2021, with the completion of COWI's detailed design scope. Gothenburg is now one step closer to having more frequent trains, shorter travel times, and less transfers for passengers travelling into the city centre.The entire West Link features eight km of double track railway tunnelling underneath central Gothenburg, and three new underground stations: Haga, Korsvägen and Centralen. COWI was engaged by the project contractor NCC to undertake a wide spectrum of consulting activities for the Centralen section, including the detailed design scope, which was completed in 2021.The Centralen portion of the West Link is progressing well and COWI will continue to support NCC, the Swedish Transport Administration (Trafikverket), and various other stakeholders with the ongoing construction works until the official opening, scheduled for 2026. The project includes a 400 m long cut & cover underground station, in a dense urban environment characterised by difficult soil conditions.The detailed design was a complex and challenging undertaking for all involved. Colleagues from a wide range of disciplines pulled together as a team, co-creating with NCC, Trafikverket and external stakeholders to ensure the final design was world class. The location of Centralen in the soft Gothenburg clay, infamous for its low consolidation rate, meant the tunnel and station experience heavy loading forces from the overlying buildings and substrate.In response to these challenges, the Centralen team presented a unique design featuring a combination of diaphragm walls and cross walls for the retaining structure, to provide greater support in the soft ground. Detailed 3D BIM models were produced of the concrete reinforcements within the structure, to provide NCC and Trafikverket with a more detailed visualisation of the site. The reallocation of existing utilities, plus the detailed design for the installation of new utilities, presented a significant engineering challenge, and demanded efficient and effective communication between NCC, Trafikverket and the utility owners, as well as with external parties working on adjacent sites.