As one of the largest shell structures in Europe, the Alster swimming hall in Hamburg is a landmark of Hamburg's post-war modernism. Its shape and concrete shell roof are reminiscent of the Sydney Opera House, which is why it is affectionately known as the Swimming Opera House.
From 2020 to 2023, the listed building underwent extensive renovation and expansion, with Lindner also involved in the construction of a special ceiling made of three-dimensionally shaped aluminium panels. A number of hurdles had to be overcome in order to reconcile the conflicting demands of a listed building with the requirements of a modern swimming hall. In addition to the heritage and anti-corrosion requirements, the new ceiling could only be attached to the existing boreholes in order to accommodate the shell roof. The roof shell and existing boreholes were digitally recorded in a very complex survey, and the aluminium ceiling was then shaped into a hyperbolic paraboloid in a separate 3D design. Lindner also clad the parapet bands with monolithic C-shaped panels made from LinCrete, a highly durable and resistant glass fibre concrete. These were matched in colour and texture to the existing fair-faced concrete structures so that the cladding blends seamlessly into the appearance of the pool.