Lausanne's topography has transformed the relationship of streets to buildings, creating the practical irrelevance of a consistent datum plane. In some parts of the city, streets are suspended and buildings buried in the ground. Buildings function as vertical passageways and bridges as multistory crossings. Moreover, the no-man's-land of obsolete industry that forms a ubiquitous buffer at the periphery of the late-20th-century city occurs, instead, in the very center of Lausanne, in the lowlands of the Flon Valley. This unusual condition allows for the implementation of the most contemporary activities in the very heart of the city.