Situated in the Eastern Alps, Austria, officially known as the Republic of Austria, , is a landlocked nation in Central Europe. Consists of nine federal states, the most populous of which is Vienna, the federal state and capital. Germany is to the northwest of Austria, followed by the Czech Republic, Slovakia, Hungary, Slovenia, and Italy to the north and east, and Switzerland and Liechtenstein to the west. With a population of almost 9 million, the nation is 83,879 km2 (32,386 sq mi) in size
At least the Paleolithic era marks the beginning of human habitation in the region that is now Austria. The Celts lived there about 400 BC, and the Romans annexed it in the latter part of the first century BC. During the late Roman era in the fourth and fifth centuries, the area was first Christianized. During the Migration Period, several Germanic tribes arrived in the area. At the close of the first millennium, Austria formed as a single state from the ruins of the Eastern and Hungarian March, initially as a frontier march of the Holy Roman Empire.