Abstract. This demonstration presents OntoDB, a prototype that allows to store explicitly in the database not only the data, but also the conceptual model defining the structure of data and the domain ontology representing the meaning of data. The demonstration illustrates three main functionalities of OntoDB: (1) a storage of a domain ontology and database content in the same repository, (2) the possibility of querying databases at ontology level, and (3) an automatic integration of heterogeneous data sources referencing/extending the same domain ontology.