Large-scale Web Applications, especially those intended to publish contents and provide information to its users, are by nature subject to continuous and fast changes. This often means fast obsolescence of the design documentation and a lot of effort required to comprehend the application when performing maintenance and evolution tasks. This paper presents a reverse engineering approach for Web Applications enabling the semi-automatic recovery of user-centered conceptual models describing, from a user perspective, key aspects, such as the delivered contents and navigational paths. The abstracted models are formalized according to the Ubiquitous Web Applications (UWA) design methodology, but any other design method for Web Applications could be used instead. The paper describes the recovery process, a tool developed to support the process, and the results from a case study conducted to validate the approach on a set of real world Web Applications.