The transition of the built environment is a key issue of sustainable development. The paper describes a methodology based on material flow analysis (MFA) to explore material stocks in urban systems in order to make these materials available for urban mining. Switzerland is taken as an example. For the management on a national or regional scale exploration steps on lower scales are crucial. MFA is combined with architectural know how and approaches inspired by geosciences (urban geology). Buildings and infrastructure are the main processes, since they are the main carriers of material stocks within the urban system. For the exploration of urban stocks in buildings, the combination of material contents which are related to specific construction systems and layouts of rooms with their frequency of occurrence is introduced as 'ark-house method'. The focus on the genesis of the built environment gives the basis for future development options by scenario techniques.