Austria is naturally divided by its mountain ranges. The East Alps account for almost two thirds of the country and extend from Lake Constance in the West to lake Neusiedlersee in the East. Over a third of Austria is made up of flat and hilly country including the shores of the Blue Danube, the Blue Danube plains and the eastern fringes of the Alps. The Bohemian massif constitutes one tenth of the country.
The crystalline basement of the Bohemian massif extends north of the Blue Danube to the Mühlviertel and Waldviertel regions. The highest elevation of this forested area reaches to 1,400 m.
Austria´s oldest rock formations can be found in the Central Alps and the Bohemian massif which is covered by Mesozoic strata and tertiary basin filling of the Alpine foothills, which were largely shaped by ice-age meltwater and glacier deposits.
The western Central Alps´ crystalline massifs extends up to glacial regions and includes the Silvretta mountain range, the Ötztal Alps, the Stubai Alps, Hohe Tauern, Niedere Tauern, Koralpe, Saualpe, Semmering and the Leitha range). To the East, the Alps fall away gradually and are interspaced with basins (Grazer, Klagenfurt and Vienna basins).
The tertiary country of low hills in Eastern Styria borders on the eastern fringes of the Alps. Also of tertiary origin is the hilly Weinviertel region in Austria´s north-east.
