The greater the impacts of our decisions, the greater the importance of the quality of our decisions. In the city governance impacts of decisions made by decision makers are enormous. This paper describes the results of our preliminary research focused on the relationship between population density and building and running costs of the city. Our attention is directed at the level of city blocks. We consider three types of buildings atrium blocks, row houses and single houses. The main aim of this article is to compare building and running costs of public spaces and the number of inhabitants using these public spaces. The differences between the building and running costs seem to be very big which can lead to a new attitude towards land use planning of our cities. The beginning is devoted also to the embedding of this issue more deeply into the field of evolution of complex systems and the key role of human decisions in this process.