The site of the Holcim Group in Holderbank today consists in a number of existing offices and laboratories, old beautiful warehouses and silos, surrounded by a very pleasant vegetation. Yet these buildings are scattered all around the area, without a real visible connexion between them. These buildings of 2-4 levels face the huge imposing volume of warehouses nearby. We feel that the whole Holcim area lacks a strong and clearly recognizable identity. We use the potentiality and existing qualities of the site to generate the extraordinary. The site is radically transformed by making use of elements from the past : existing offices buildings, warehouses and concrete silos. All the existing structural buildings are kept and connected together by a new entity, a global building strongly marking Holcim's identity and making its historical presence visible. The existing important trees are also conserved. The vegetal presence is enhanced and clarified. The idea is to recycle and reuse, to make things last, to avoid the waste of energy, cost or material by using simple robust construction and climatic devices, in a global philosophy of economy and simplicity as a sustainable approach. In the same way, our proposal is long-term aimed and anticipates future evolutions and needs. Prefabricated concrete is an ideal construction material to achieve vast surfaces for a multiple possibility of uses, rapid cost effective construction, and delicacy towards the existing elements. This unusual use of concrete with a radical sustainable approach provides a very visible signal building for Holcim Group as a manufacturer of sustainable construction materials. We create a ten meters high table which connects the existing buildings together and runs across the entire site. It forms the roof of a huge volume with a polycarbonate facade, creating a first envelope and intermediate climate between exterior and interior. It functions also as a support for a second light envelope and second intermediate climate, made of industrial greenhouses. The program takes place in those two semi protected environments which temperature and light can be controlled through simple automatic devices (opening, shade).