The database usability experience has shown that visual query languages tend to be superior to textual languages in many aspects. By applying this principle in the context of ontologies, we present OntoVQL, a graphical query language for OWL-DL ontologies. OntoVQL maps diagrammatic queries to DL based query languages such as nRQL, which is offered by the OWL-DL reasoner Racer. OntoVQL hides the complexity of the DL query language from users and allows them to query OWL ontologies with less difficulty. A visual query system equipped with this language has been implemented and is now available. This tool enables users to formulate queries incrementally by having more than one query simultaneously available for getting combined or broken down into new queries. Giving instant feedback in the form of result cardinality is another important feature of the tool that helps guiding users into building meaningful queries.