Maps of physical environments and geographical areas are pervasively exploited in many human activities. Electronic maps of virtual worlds have been studied and proven to be useful as navigation aids to help users in finding their way through the 3D world. The contribution of this paper is twofold. In the first part, we propose an automatic method for the derivation of electronic maps from Web3D worlds which is based on standard X3D/VRML nodes, and can thus be run by any X3D/VRML browser. In the second part, we discuss how we are using the proposed method for the study and support of users' navigation in virtual worlds. In particular, we show: (i) how the derived maps simplify the implementation of various navigation aids, and (ii) how we are using the derived maps to visualize usage data from users' visits to 3D Web sites. CR Categories: I.3.6 [Computer Graphics]: Methodology and Techniques -- Interaction techniques. I.3.7 [Computer Graphics]: Three-Dimensional Graphics and...