The "International Geological Congress" (IGC) took place in Vienna in 1903, during a period when the city became a metropolis and experienced its greatest population growth. Hosting the congress was important for the self-assurance of the Habsburg earth scientists. As a sign of continuity, the IGC was part of the institutionalization process and took place every three years with the first conference being held in Paris in 1878, the following in Bologna (1881), Berlin (1885, delayed by one year due to an outbreak of Cholera), London (1888), Washington D.C. (1891), Zurich (1894), St. Petersburg (1897) and Paris (1900).Both the scientists and the government of the Habsburg Monarchy considered geology as an unifying force of progress within the multi-ethnic state. The first geological map of the entire Monarchy, pre-pared by the Imperial Geological Survey ("Geologische Reichsan-stalt", GRA founded in 1849) and published in 1867, can be seen as an expression of this unifying goal. From today's historical perspec-tive, the political structure of the Habsburg Monarchy is referred to as a "composite state", and we may argue that the geological map of the entire Monarchy created an expressive, unifying sign. During the 19th century, geological research within the empire reached its peak with substantial and highly diverse output being achieved in Vienna and other cities of the Monarchy. These efforts had long been determined by the attempt to clarify the alpine structure, for which the future "Deckenlehre" (nappism, theory of overthrust faulting) would repre-sent a "magic key" (Tollmann, 1973, 31). The standing of the high level of Habsburg earth science expertise amongst the leading European powers had to be defended, and the IGC provided the ideal opportunity to assert this claim of excellence.On August 19, 1,903,664 members from 29 countries were registered, 393 joined the congress in person. 23 women were registered, all being spouses of the participants. Although the number of partici-pants did not represent an increase compared to the previous event in Paris in 1900, which had been attended by 461 geologists, it should be borne in mind that in Paris the World Exhibition, which was tak -ing place at the same time, was an added major attraction. The next geologists' congress in Mexico in 1906 only attracted 321 attendees. The spatial distance was decisive for the decline in numbers, since the partici-pants from Europe traditionally formed the majority.Formally, the organization in Vienna followed the given structure of previous congresses. A preliminary Executive Committee and a broader Committee for Organization was established in Vienna in 1900. In terms of content, three groups of topics were favoured, (1) the ques-tion of crystalline shales, (2) that of nappe outlier (klippen) and (3) research on "Balkan and Orient". With the realization by scientists of a greater extent of the over-thrust phenomenon ("uberschiebung"), the congress had brought about a turning point in the recognition of the schist cover theory "Deckenlehre" (Alpine nappism, theory of overthrust faulting).A total of 41 scientific papers was presented. Through 48 articles as guides prepared for 21 excursions the Habsburg Monarchy presented itself to the geological community in its territorial entirety, as a great power of considerable geographical size and range. On the occasion of the congress the monumental work "Bau und Bild osterreichs" was published, based on the cooperation between the leading Austrian geologists Carl Diener, Rudolf Hoernes, Franz E. Suess and Vik-tor Uhlig. Eight maps and 250 images were included to illustrate this masterpiece (Diener et al., 1903) with a very important preface by Eduard Suess.The focus of the congress on the Balkans was indicative of the geo-political component and underlined the scientific strength of the Habsburg Monarchy in this space. If there was one thing that surpassed all pre-vious IGC congresses, it was the high number of 21 excursions offered, which concerned the most interesting and geologically diverse areas of the monarchy.The venue of the IGC was the University of Vienna with events and sessions held in both its large and small festivity halls (Festsale) while some presentations were also given in lecture halls at the Department of Geology.For each individual excursion, 48 accompanying texts were drafted and combined in a guidebook with 1,190 pages in total (Fuhrer, 1903). All results, papers about debates and excursion programmes were published in a handsome volume, which clearly stood out from previous IGC publications thanks to its comprehensive coverage of the congress (Compte rendu, 1904). In addition to the stimulating discussions following the presentations, the excursions also contributed to the success as they underpinned the high standard of Habsburg earth sciences within the European and international context.The steadily growing internationalization over the course of the 19th century had several faces. In the geosciences, it was the IGC from 1878 onwards, which, alongside other forms of communication, consolidated already existing international networks. In addition, international visibility, national public reputation and honour wereessential drivers. Industrialization and urbanization formed the back-ground to this specific internationalization process.
