The fundamental reason for the existence of cities is that they enable high accessibility. High accessibility is associated both with economic gains such as higher wages and productivity and opportunities to satisfy specialised interests and lifestyles. The history of human civilisation is a history of urbanisation. Scientific and cultural progress rest on two cornerstones: one is the written language, enabling us to communicate innovations and experiences over distance and time; the other is cities, which have always been our engines of innovations and discovery. Since the demand for and the rewards of high accessibility have accelerated over the last two centuries, this has fuelled urbanisation at an ever higher pace.