Vienna is the capital and largest city in the Republic of Austria. Founded sometime around 500 BC, Vienna was originally a Celtic settlement. In 15 BC it became a Roman frontier town, fortified to guard the empire against raids from the Germanic tribes to the north. The Romans remained in the city until the 5th century AD, when they mysteriously abandoned the city, perhaps vacating because of a catastrophic fire occurring at that time.
The city became the home of the Babenberg Dynasty during the early Middle Ages, and in 1440 it also came to be the resident city of the Habsburg Dynasties. During the next few centuries it grew into a center for the arts, science, and fine cuisine, and eventually became the capital of the Holy Roman Empire. The city remained a formidable fortress during its cultural growth, and stopped the Ottoman armies twice at the Siege of Vienna in 1529 and in the Battle of Vienna in 1683.
After the collapse of the Holy Roman Empire, Vienna continued its collection of capital titles when it became the capital of the Austrian Empire in 1804. The city continued to grow dramatically and many suburbs and surrounding towns were incorporated into its boundaries.
The city played little part in World War I, but did become the capital of the First Austrian Republic after the collapse of the Austro-Hungarian Empire. It was a bastion of socialism in Austria (earning it the nickname "Red Vienna") until Adolf Hitler occupied the city in 1939. For the first time in centuries, Vienna lost its capital status to Berlin, but quickly regained it after the Second World War when it was once again named the capital of Austria. During this period Vienna became a hotbed for international espionage between the West and the Soviets.
In the 1970s the Austrian Chancellor created a new area in the city to host its growing international institutions, aptly named the Vienna International Center. Vienna now hosts an office of the United Nations, the International Atomic Energy Agency, the Organization for Security and Cooperation in Europe (much to the dismay of the spies), and many other international agencies. While Vienna is famous for its elaborate balls, museums, and operatic tradition, one of the most well known 'exports' of the city is the culinary dish Wiener Schnitzel, a breaded and fried cutlet of veal. The canned product "Vienna Sausages", however, is a purely North American invention.