At the Archive of the History of Geology at the University of Vienna exists a partial estate of Eduard Suess, the first professor for Palaeontology and Geology at the University. A very interesting, drafted and coloured document is a cross-section between the medieval towns of Eggenburg and Horn, 60 km north of Vienna. The creation of this cross-section can be dated back to the years between 1859 and 1862. Suess also mapped the sediments of the "Eggenburg Sea" in the area (Tertiary, Miocene age). The names of the fossils deposited in the "Eggenburg Sea" were listed by Eduard Suess during his fieldtrips in this area. They bear witness to the theory of sea level movements-eustatic sea level movements-developed by Eduard Suess. Here he formulated his first ideas about an ancient sea, later named Tethys.