The restructuring of 175 Haussmann as part of the PCA-STREAM “urban metabolism” vision: reinterpreting Parisian architecture to build the city upon itself. 175 Haussmann had to respond to the changes in the way we work. The project thus pays particular attention to the design of service spaces, in the spirit of hotel lobbies, but also to furniture, which refers to aesthetic codes that are more domestic than purely tertiary. PCA-STREAM brings together two buildings, designing a new circulation core which brought about fluid and open floors offering a non-hierarchical horizontal distribution of teams. Widening the central courtyard has created a bright, convivial common space, housed under a large, triple-height glass dome. The restructuring was designed to foster a reconnection of the building and its users to nature. The windows are designed to be opened on the terraces and allow for natural ventilation, while an innovative dioptre façade reflects the natural light to the very bottom. With an exceptional panoramic view on Paris, the liveable landscaped terrace offers a wealth of uses in tune with the seasons, bringing a sensory dimension of biophilia to the complex. This green roof terrace uses an innovative vertical urban permaculture: a hydrological membrane as a vertical greening tool supports a complete ecosystem fed by organic matter, where micro-organisms and plants live symbiotically. The landscaping system optimizes management of the water resource, in particular through the integration of a greywater treatment system using the phyto-purification potential of plants. PCA-STREAM relied on the idea of raising the construction through the glass roof, characterized by its photovoltaic glass scales. It gives the identity of 175 Haussmann by integrating a contemporary feature into the historical and heritage context of the district. This singular space, midways between interior and exterior, becomes a tool for community-building.