ICONVIS (Interactive and Customizable ONtology-based VIsualization System) is a Rich Internet Application that allows to display and browse structured data in the form of an ontology. The ontology in input to the system is designed based on the most significant values of a data source, so it is a representation of the overall knowledge of the data domain. Users can switch from the exploration of concepts in the ontology graph to the effective fruition of contents of the data source. In addition, ICONVIS is able to reach open datasets on the Web (like DBpedia, Geonames, Freebase, etc.) in order to increase information at runtime and to display it to users in a suitable fashion.