Austria, officially the Republic of Austria, is a landlocked country of roughly 8.3 million people in Central Europe. It borders Germany and the Czech Republic to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the west. The territory of Austria covers 83,872 square kilometers (32,383 sq mi), and has a temperate and alpine climate. Austria's terrain is highly mountainous due to the presence of the Alps; only 32% of the country is below 500 meters (1,640 ft), and its highest point is 3,797 meters (12,457 ft). The majority of the population speaks German, which is also the country's official language. Other local official languages are Croatian, Hungarian and Slovene.
The origins of Austria date back to the time of the Roman Empire when a Celtic kingdom was conquered by the Romans in approximately 15 BC, and later became Noricum, a Roman province, in the mid 1st century AD—an area which mostly encloses today's Austria. In 788 AD, the Frankish king Charlemagne conquered the area, and introduced Christianity. Under the native Habsburg dynasty, Austria became one of the great powers of Europe. In 1867, the Austrian Empire was reformed into Austria-Hungary.
The Austro-Hungarian Empire collapsed in 1918 with the end of World War I. The First Austrian Republic was established in 1919. In the 1938 Anschluss, Austria was occupied and annexed by Nazi Germany. This lasted until the end of World War II in 1945, after which Austria was occupied by the Allies and its former democratic constitution was restored. In 1955, the Austrian State Treaty re-established Austria as a sovereign state, ending the occupation. In the same year, the Austrian Parliament created the Declaration of Neutrality which declared that the country would become permanently neutral. Austria was the only country to be (partly) occupied by the Soviet Union in the post WWII era to hold free elections and avoid authoritarian Communist rule by forced decree from Moscow.
Today, Austria is a parliamentary representative democracy comprising nine federal states. The capital—and with a population exceeding 1.6 million, Austria's largest city—is Vienna. Austria is one of the richest countries in the world, with a nominal per capita GDP of $43,570. The country has developed a high standard of living, and in 2008 was ranked 14th in the world for its Human Development Index. Austria has been a member of the United Nations since 1955, joined the European Union in 1995, and is a founder of the OECD.[ Austria also signed the Schengen Agreement in 1995, and adopted the European currency, the euro, in 1999.