Open Government Data initiatives and particularly Open Government Data portals have proliferated since the late 2000’s. A comprehensive analysis of the capabilities and potential of these initiatives is currently missing from the recent research literature. In order to address this gap, the paper at hand aims towards analyzing the landscape of Open Governmental Data in the European Union from a functional, semantic and technical perspective. Our research focused on the collection and categorization of an indicative number of public data sources for each of the 27 European Union country-members through investigating their services and characteristics. By modeling and classifying the data sources according to their key attributes, we were able to proceed to their statistical analysis and assessment in terms of their content, licensing, multilingual support, acquisition, ease of access, provision and data format. Our results portray the current quality of Public Sector Information infrastructures and highlight what still needs to be done in order to make public data truly open and readily available for researchers, citizens, companies and innovation in general.