Most aggregators face challenges regarding searchability, discovera-bility and visual presentation of the content due to metadata heterogeneity. Fully automated enrichment in most cases is not sufficient. We developed semantics.gr, a tool for massive semantic enrichment and contextualization of content that combines a curator/expert metadata mapping suite with a self-improving auto-matic suggestion mechanism. We subsequently used this tool in order to enrich the content of searchculture.gr, the cultural heritage aggregator of National Documentation Centre (EKT). The results were substantial allowing us to improve drastically the quality of search and navigation of the aggregator’s portal.