Urban land is developed, utilised, abandoned and left to degradation in many different ways. These processes are closely related to four aspects of human activities: the extraction of resources, their transformation into goods, the production of waste and the conflicts that arise when population grows and demands increase while resources remain limited. Urban land is developed and deteriorates in the course of these activities, while cities keep spreading, consuming the green spaces surrounding them. Sustainable city development aims at protecting the environment by reusing urban terrain. The author brings together the different aspects of this transdisciplinary endeavour by discussing the causes of degradation, the strategies of investigation and the techniques of remediation of urban land.