OpenDataMonitor brings open datasets to light. As a platform, it gives visitors an overview of available open data resources, allowing them to analyse and visualise existing data catalogues using innovative technologies. The framework harvests datasets, collecting metadata from diverse open data sources. The harvested metadata is then harmonised, in that the gathered information is structured and processed. Scalable analytical and visualisation methods allow end users to learn more about the composition of regional, national or pan-European open data repositories. For example, the aggregation of catalogues of one region or country can be easily visualised to draw an exact picture of the open data situation and allow comparison to other areas. Analysing and visualising metadata will reveal hidden potential and essential insights from existing resources and identify gaps where additional open data are needed. Our work was based exclusively on open standards, with emphasis on those formally adopted by the European Commission. In the OpenDataMonitor project we adopted CKAN as the underlying software architecture within which all our software contributions are integrated as plug-ins.