 Particularly in the 19th century, Vienna General Hospital was the center of the Viennese Medical School, as one of the centers of medical research.Thus Ignaz Semmelweis made his observations of hygiene, and Karl Landsteiner discovered at the AKH the groups of blood types.The site of the old AKH is used as the main university campus of the University of Vienna, and includes the university's medical institutes as well as numerous humanities institutes and several catering trade enterprises and smaller enterprises.