One of the hardest points in context-aware applications is deciding what reactions a system has to a certain context. In this paper, we introduce an architecture used in two context-aware museum guides. We discuss how the context is modelled and we briefly present a rule-based mechanism to trigger system actions. A rule-based system offers the flexibility required to be context-sensitive in the broadest sense since many context features can be considered and evaluated at the same time. This architecture is very flexible and easily supports a fast prototyping approach.