Affordances are an important basis for many human-environment interactions such as navigation or geo-design. In this short paper we present an approach to modelling affordances based on treating affordances as emergent phenomena in an agent-based simulation. We use the notion of an affordance schema to represent the setting in which the emergence of an affordance is made possible. We use a case study to show that (unexpected) affordances emerge during the course of the simulation. While the general approach is promising and may be used for other emergent phenomena such as landmarks, we also acknowledge and discuss the problems incurred during the modelling process. The paper closes with a reflection and some ideas for future work.