In the last years one of the main concerns of the software industry has been to reengineer their legacy Web Applications (WAs) to take advantage of the benefits introduced by Rich Internet Applications (RIAs). In this context, Model Driven (MD) Web Engineering approaches have been extended with new modeling primitives to obtain the benefits provided by RIA features. However, during the last decade, widespread language-specific Web frameworks have supported actual Web system development. In this paper we present a MD reverse engineering process to obtain a conceptual representation of the navigational concern of a legacy Web application (LWA), as an initial step within a LWA-to-RIA modernization process. WebML is selected as the target MD Web Engineering approach.