This paper presents the Evospaces reverse-engineering tool that represents the architecture and metrics of complex software systems in a 3D virtual world. The main goal of our project is to exploit familiar metaphors (analogical representations borrowed from another domain) and sophisticated interactions modes to help the user understand complex systems. First, we present the general architecture of the Evospaces tool. Second, we show the metaphors we have implemented to help the user to quickly get an overview of a complex system. Then we present the interaction mode we designed to let the user explore such a complex system. Finally, we show an example of a virtual space we have designed to represent the architecture of Mozilla. We conclude with an account of our current research directions. The main contributions of this paper are the metaphors that we have used and the types of interaction modes we have implemented. They represent a real contribution to the set of tools that can he...