groups broke away leaving Austria's current boundaries as German Austria, which was proclaimed an independent republic. The severe global economic crisis coupled with domestic political tensions led to civil strife in February 1934, with the May Constitution of 1934 resulting in an authoritarian corporate state. Just two months later the Austrian Nazis staged the July coup, wanting to annex the country to into Nazi Germany, resulting in the assassination of Chancellor Engelbert Dollfuss. While the coup failed, Adolf Hitler succeeded in annexing Austria on 12 March 1938 as Ostmark, until 1945. Austria was divided into four occupation zones after the Second World War and then in 1955 became the independent sovereign state (Second Republic) that has existed to the present day. In 1995, Austria joined the European Union. Geography and geology The modern state of Austria is considered to have three geographic zones. The biggest consists of the Alps, which covers 62.8% of the country's landmass. In the north, across the Danube, is the Austrian (southern) portion of the Bohemian Massif, called the "Böhmerwald" or Bohemian Forest, a relatively lower mountain range of granite that makes up another 10% of the Austrian land area. The remaining parts of the country are the Pannonian lowlands along the border with Hungary (11.3%) and the Vienna Basin (4.4%). The Bohemian Massif and its foothills were formed in the Variscan orogeny of the late Paleozoic era. Another important element of Austrian geology and geography is the late Mesozoic Alpine orogeny, and the subsequent formation of the Paratethys ocean and Molasse Basin in the Cretaceous era. The extensive alpine regions are sparsely populated, and form a barrier to the passage of peoples apart from strategic passes providing access to Italy. Austria is positioned between the eastern European countries and central-western Europe, a position that has dictated much of its history. The Danube Valley has always been an important corridor from the West to the Balkans and the Orient. Prehistory Paleolithic The Alps were inaccessible during the Ice Age, so human habitation dates no earlier than the Middle Paleolithic era, during the time of the Neanderthals. The oldest traces of human habitation in Austria, more than 250,000 years ago, were found in the Repolust Cave at Badl, near Peggau in the Graz-Umgebung district of Styria. These include stone tools, bone tools, and pottery fragments together with mammalian remains. Some 70,000-year-old evidence was found in the Gudenus