Environmental issues such as sustainability, the protection of resources or reducing emissions have long been the focus of politics, industry and the economy. High time, then, to examine their role in the world of architecture more closely. The recycling, and with it the re-introduction of materials into the cycle of matter takes place in different forms in the construction industry. The projects presented in the magazine range from the recycling of entire building components (e.g. from concrete), to the use of waste products (e.g. wood) and demolition waste (e.g. stone) or even the completely invisible use of recycling materials like façade panels made from old glass. In the »Discussion« section, chemist M. Braungart describes the principle of »cradle to cradle«, which questions ecological efficiency and calls instead for intelligent design. He believes that products must be designed so that instead of becoming waste at the end of their lifetime, they can be used to create new things. He shows how this can be done in architecture with several already completed examples.