Between 1973 and 1985, a group of art historians of the University of Leiden prepared the final publication of H. van de Waal's Iconclass, an iconographic classification system. Iconclass is a classification system designed for art and iconography. It is the most widely accepted scientific tool for the description and retrieval of subjects represented in images (works of art, book illustrations, reproductions, photographs, etc.) and is used by museums and art institutions around the world.
The Bildindex combines image records from over 80 cultural and scientific European institutions - museums, historic preservation offices, libraries, university and research institutes. The records detail the objects' provenance, physical properties, related collections and much more. It's a valuable resource for cultural heritage research as well as art and architecture
The Digitaler PortraitIndex provides access to a wealth of Early Modern European prints.