Raise the chalices

Long divided by surface rail lines, Stuttgart has been "stitched back together"-topographically, socially and ecologically-thanks to a bold intervention that, by bringing tracks from the Central Station underground, frees the street level and allows the extension of the Schlossgarten park. Conceived by Christoph Ingenhoven and steadily developed and refined together with the architects of Ingenhoven Associates and a select group of engineers, the project stems from a deep understanding of geometry, a refined sense of light, atmosphere and form, and a shared intuition of the holistic potential of the site. In close collaboration with Deutsche Bahn and the City of Stuttgart, the station is thus presented as a synthesis of public ambition and technical mastery.

The centerpiece of the project is an extraordinary structural system: 28 concrete "goblets" emerge in the new lobby, supporting a luminous roof. The roof, a continuous field of anticlastic surfaces, stretches 420 meters long and 80 meters wide, reaching a height of 12 meters above each dome. It appears as a unique, sculpted continuum: monumental yet fluid, technical and harmonious. Made of exposed white concrete, the chalices serve both as structural supports and as tools for delineating space. Each creates a circular oculus in glass and steel, capturing natural light and diffusing it deep into the hall below. Behind the apparent simplicity lies a careful process of digital modeling and structural analysis: each curve follows the natural path of forces, balancing tension and compression according to a geometric logic. The result is a harmonious union of light, air and matter, where structural clarity translates directly into strength. In addition to its strong sculptural impact, the roof functions as an intelligent climate system. From the park side, the chalices inhale fresh air, which heats up and rises through the domes, creating a continuous natural flow. This passive process, supported by geothermal exchange under the tracks, keeps temperatures constant throughout the day. Photovoltaic panels around the perimeter of the roof and on the facades generate renewable energy, while wells and radiant systems provide indoor comfort. Domes serve simultaneously as skylights and ventilation towers, allowing the lobby to rely on no mechanical cooling or artificial light during the day.

The station roof allows the Schlossgarten park to extend along the old railroad track, connecting the Mitte and North districts along the Stuttgart basin boundary. Moving the tracks underground created one of the largest urban redevelopment areas in Europe, effectively doubling the size of the city center. On this reclaimed land, the Rosenstein district emerges as a climatically responsive model: a compact district of housing, culture, research and work, organized around tree-lined boulevards, courtyards and public squares. Soft mobility, renewable energy and water management define its structure.

With the tracks moved underground, the Bonatzbau is no longer an operational terminal, but becomes a metropolitan gateway. New underground platforms, oriented east-west, replace the previous cul-de-sac configuration, increasing capacity, safety and efficiency. This shift frees up the surface for public spaces and parks, while under the vaulted concourse high-speed, regional and local systems meet in an integrated node, connecting Stuttgart beyond the metro network. The project reinterprets Paul Bonatz's historic 1928 building as part of an architectural continuum. The massive stone facades are preserved, their tectonic clarity creating a counterpoint to the fluid geometry of the new lobby. Selective openings and passageways ensure visual and spatial continuity between the original structure and the hall below, allowing the historic volume to transform into a city foyer connecting park and center. Inside, functions are reinterpreted through adaptive use: exhibition areas, services and public spaces enliven the spaces while preserving their material integrity. The dialogue between the tactile weight of masonry and the luminosity of new concrete surfaces brings together a century of engineering thought.

The interaction between light and matter defines the emotional register of architecture. The domes act as optical instruments, filtering light and diffusing it over the roof surfaces with varying intensity. The changing sky thus becomes an integral part of the building. Even on cloudy days, the white concrete retains a discreet radiance, an almost musical echo that unites structure and atmosphere. The station is both a gesture of departure and arrival, movement and pause. The vaulted hall, conceived as a continuous field, generates an inverted landscape of light, form and material presence: a monumental and harmonious space at once. From the first sketches to the delicate models made from soap film to the precision of digital simulation, each stage of realization seeks clarity, proportion and grace.

The chalices of the Central Station represent the structural heart of the project. Their geometry stems from digital optimization models that simulate the natural path of forces, light and airflow. Parametric control of curvatures and thicknesses minimizes the use of materials while still ensuring proper transfer of loads between the drums and connecting slabs. Manufacturing follows a data-driven modular flow: a single model generates all chalice variants, standardizing joints, anchor points and segments to enable efficient reproducibility. CNC-milled panels, machined from cross-laminated timber, are assembled with reversible joints and coded identifiers. Digital traceability allows the structure to be fabricated, tested and created with extreme precision, achieving the SB4 exposed concrete finish without further treatment. The research program Stuttgart 210 - rethink, rebuild, initiated by the University of Stuttgart, extends this digital logic to the entire materials cycle. Once the 28 chalices are completed, the wooden forms are disassembled, digitally cataloged, and prepared for reuse in new constructions. Early experiments demonstrate their second life in civic prototypes as small community facilities. Through the integration of advanced modeling, modular fabrication, and reuse strategies, the chalice development transforms a highly specific form into a repeatable and adaptable building system. The process demonstrates how optimization can increase accuracy and speed, extend the life of materials, and harmonize performance, manufacturing, and circular design into one coherent method.

The station serves as a strategic hub between Paris, Vienna, Zurich, and Milan. The east-west axis strengthens Stuttgart's position in Europe's main high-speed corridor, reducing travel time and enabling zero-emission long-haul mobility. The new configuration combines technical performance and collective ambition: by moving the infrastructure underground, the project reconciles continental connection and local quality of life. What began as a transportation initiative has evolved into a European model of sustainable mobility, merging technical and cultural significance.