This paper presents EnViz, a prototype software application for the visualization of environmental data. The rationale for the development of the application is given, together with the methodology for collecting the data. A technical description of the software is provided, with a presentation of new features and their relevance. Two case studies are presented, and their relevance in the testing of the software is discussed. Visualization results from the application of the software are included. Particular attention is paid to the testing and evaluation of the application by real users. The methodological approach is described and the results of the tests are presented. The paper concludes by interpreting the results and pointing towards directions for further research on the topic.