Over the course of the last century there have been significant changes in the practices of archives driven by the massive increase in the volume of records for archiving, a larger and more diverse user base and the digital turn. This paper analyses work undertaken by the European Holocaust Research Infrastructure project (EHRI) to develop heritage archives into research infrastructures by connecting their knowledge and making it relevant for research. In the paper, we focus on EHRI's work on an integrated collection portal; acting as a central gateway to the rich information on Holocaust-related sources. At the time of writing, the portal contains over 150,000 descriptions of over 1,850 institutions that hold Holocaust-related archival material in 51 countries. In addition, it hosts a range of other services, concise reports that provide in-depth per-country information about the Holocaust history and archival situation in 47 countries as well as research guides. The paper presents how the EHRI portal work connects to the state-of-the-art of heritage portals and the novel solutions we had to develop to align the portal with the requirements of a research infrastructure.