The "province west of the Enns river" is characterized by three different types of landscapes.
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In the north there are granite and gneiss hills, separated in the middle of the province by the Danube valley from the Alpine foothills, the limestone Alps and the Upper Austrian Salzkammergut.
The Mühlviertel is a truncated upland, formed by the crystalline of the Bohemian mass, the oldest mineral found in Austria. The Alpine foothills south of the Danube were formed during the tertiary period, when the crystalline and the Alps were separated by the trough of the molasses sea. Later the trough was filled by the gravel of the rising mountains and the Bohemian mass. Glacial river gravel now cover the tertiary deposits of the Alpine foothills. To the south we find the North Limestone Alps with the Sensengebirge, the Höllengebirge and the Totes Gebirge mountain ranges. At the base of the Limestone Alps lie the salt mines of Bad Ischl and Hallstatt, which were formed in salt pans by the evaporation of sea water.
